I had nothing but issues with 10.3r3 and 10.3r4 when it comes to delta updates mainly. I was always rolling back to 10.3r1 or even earlier releases for AP122s. Not sure why is that. But then I tried to review a list of recommended releases and couldn't find XIQ there on the dropdown (https://www.extremenetworks.com/support/compatibility-matrices/sw-release-extremexos-eos/). I tried to use GTAC KB method but it didn't show me stuff either: https://extremeportal.force.com/ExtrArticleDetail?an=000084460
Is there a current list of recommended/stable IQEngine release for APs?
I too suspect I may be having ongoing firmware issue on some of the latest versions, however when I recently submitted a GTAC ticket with techdata after having an issue, I was told to update from 6.5r14 to 6.5r16 as "It is possible 6.5r14 is attributing to the negative behavior, and ensuring the AP is on the latest OS is a good step to start in troubleshooting the behavior". When I pushed back saying there are no listed known issues documented for 6.5r14, and no fixes listed on documentation for r15 or r16 GTAC said r16 is the latest and recommend version. It seems to me regardless of the fact that these firmware's have ongoing and repeated undocumented bugs, it would seem GTAC is being told to get customers to the latest firmware before helping troubleshoot. This is frustrating as I know some of the older firmware is more stable, and that based on forum feedback, many customers are holding out on older firmware due to ongoing (often serious) issues with newer versions.
I'd love to also see the list you've asked for but I wouldn't hold my breath. They seem to be quite tight lipped regarding ongoing issues in firmware, and never update release notes with updated information.