We have identified an issue in the latest firmware for the APEX Pro and VERTIX - v 3.0508.0 released 7 Aug 2024. Regretfully, the issue affects the accuracy and integrity of speeds being recorded by the APEX Pro and VERTIX. We recommend that APEX Pro and VERTIX users do not upgrade to firmware v 3.0508.0. 

Users who have already upgraded, but own another verified device are requested to post from that device when possible. Our tech crew, supported with technical expertise from our community is actively working with COROS to get this issue resolved ASAP, and we will keep you updated.  For now we advise to avoid competitions to run on max 2s speed or on single 10sec runs, we recommend to use the 5x10s AVG or 500meters instead.

GP3S Crew

I have tried to illustrate the issues by driving around a short test circuit; 3 laps with total distance of 5 km. These show what is "normal" for these firmware releases but much bigger issues are evident in real session data.

https://logiqx.github.io/gps-details/devices/coros/windsurfing/

My advice would be to avoid any firmware release since May 2024 - 3.0408.0 / 3.0409.0 upwards, especially 3.0508.0 on the APEX Pro / VERTIX. If you have an APEX Pro or VERTIX, you can downgrade to a working firmware (3.0309.0) using the instructions at support.coros.com/hc/en-us/articles/15344945273620-How-to-manually-update-my-COROS-watch

I've not managed to downgrade my APEX 2 Pro (yet), although I believe it should be possible. If anyone has any luck downgrading their APEX 2 / APEX 2 Pro / VERTIX 2 / VERTIX 2S then please let us know how to do it.

Just bought a new Coros yesterday, especially for this site. Does this issue also include the Apex2Pro and Vertix2?

The APEX 2 Pro and VERTIX 2 are affected, but to a lesser extent than the APEX Pro and VERTIX.

Be sure to use all systems or dual frequency (not regular GPS) to minimise the effects.

If you are on firmware 3.0309.0 (or earlier) then it is advisable not to upgrade, until COROS resolve the issue.

COROS are aware of the issue and working on a fix.

Is there anything new about the faulty firmware 3.0508.0?

I wanted to downgrade but I can't open this page --> support.coros.com/hc/en-us/articles/15344945273620-How-to-manually-update-my-COROS-watch

Apparently I'm not authorized to open this page?!
Can someone send me instructions on how to downgrade please.

Many thanks in advance!

Tech crew just received a new beta, we will test this one this week, will share info asap. 

I've update to Beta FW 3.0707.0
Yesterday I used this new version in Speedsurfing mode and I was not happy with the numbers I got
Display and upload on GP3S where the same, but not what I expected.
Some numbers
Fit/GP3S : 40,28kts (74,6kph) avg
GPX : 42,45kts (78,61kph) avg
Reverence is a Gyro with raw UBX logging : 41,67kts (77,19kph)

Posted logs : https://www.gps-speedsurfing.com/default.aspx?mnu=forum&forum=2&val=220858

Thnx for reporting, we also noticed this with the Vertix 2S and reported this back to Coros. The build for Apex provided much better data and brings the Coros devices back on the same level (and even a bit better) in comparison with the May software deployments. Please forward also the raw .UBX data and .FIT from the Vertix 2S to info@gps-speedsurfing.com , so we can share it with Coros. 

To clarify the 3.070x.0 beta release(s) have re-introduced the May issue for the Vertix 2 / 2S. This has been documented at https://logiqx.github.io/gps-details/devices/coros/smoothing/

The APEX 2 and APEX 2 Pro have improved significantly in the 3.070x.0 beta release(s), suggesting they failed to implement the same patch on the 4 newer models. The older APEX Pro and VERTIX still require a fix for the problem which was introduced in v 3.050x.0.

Anybody concered about the accuracy of the speedsurfing mode on their COROS can of course log a call with COROS. The product team have been provided with numerous articles that I've written about the issues - https://logiqx.github.io/gps-details/devices/coros/

Differences between the GPX and FIT are because there is no universal standard for speed in GPX 1.1 files. The COROS approach is not supported by all software that reads GPX files, hence the apparent differences between GPX and FIT.

So Corors decided to no longer support Vertix 1, APex pro etc - no more firmware updates.
https://support.coros.com/hc/en-us/articles/30226328392724-Firmware-Status-Update-PACE-2-APEX-Pro-VERTIX-1
They release a version that doesnt work, remove tha possability to go back to the may-release send out a new releaae that deosnt work either and then decide not to give out any new firmware releases? Is this even a seriuos company? 
Are we making it easy for windsurfers to understand and do speed windsurfing when these things happen? What device should you buy, which are ok to use?

As stated by Michael George, please report these issues to Coros directly. From our side we are still working with Coros to see what can be done to get this fixed. The tech crew is also working on alternatives, we expect to share more info on this before the end of this year.

Fortunately, it is possible to revert the APEX Pro and VERTIX back to firmware 3.0309.

COROS have removed the instructions from their website, but I've copied them to this page:

https://logiqx.github.io/gps-details/devices/coros/firmware/downgrade.html

The links to the firmware still work. Should they stop working in the future, I will upload the files to GitHub.

I see that a number of the guys in Luderitz still use the APEX Pro or VERTIX.

It is very unfortunate that these devices cannot be trusted with firmware 3.050x.0, especially 2 seconds.

It been 3 months since the problems with 3.050x.0 were first reported and no fix, or news about a fix.