The only Wi-Fi related commit is
https://github.com/koreader/koreader/pull/8942, and that landed *in* 2022.03.1

. (So I'm going to need clarification on what "the latest stable" exactly means for you, and whether your experience differs between 2022.03 and 2022.03.1

).
The only major change is the autostandby feature, but that is opt-in (and a terrible idea anywhere else than on an Elipsa or a Sage), so did either of you happen to enable it?
There's even *less* changes between -37 and -38 (as the number implies, only one, actually ^^).
As usual, can't tell you much more without verbose debug logs.