I've seen cases in which downgrading to older 25.x releases helps with stability on the older AP's. It's often case by case based on config and usage.
The last case I see on this opened by you was Dec 2020. Perhaps open a new case online and request a downgrade to 25.14 to test stability. You could have Support downgrade just a single AP (or however many you want) to the older release so you can contain the testing to an area before downgrading all AP's.
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