I have such a problem. After the last major update of my watch (R890XXU1GVH2 / R890OXM1GVH1 - September 2022) I noticed a malfunction in airplane mode. I turn it on when not using the device to save some battery. And everything worked as it should for half a year.
Well, after the update, after turning on the airplane mode, the watch seems to disconnect from the phone, but not always (?!) or when I check it, it is connected again after some time. And there is an airplane icon on the watch, but no autonomous mode icon (crossed-out phone). And the Bluetooth icon on the phone is lit and the watch is normally connected (Galaxy Wearable sees it as connected). Before the update, there was no problem with this, so obviously something is wrong. Airplane mode should turn off all radio modules!
The smaller watch (also Classic 4) of my wife after the update does not have this problem (once or twice only the screen flashed strangely). I have not reset my watch - I do not want to do this because I have everything set up.
Has anyone seen a similar problem? I have a Note 10+ phone, but I don't think it mattered what phone is paired.
I have the same problem.
I tried also to go into the settings, then into connection and diseable bluetooth. It was seemed to work but after a moment my bluetooth turn back on automatically, like you said. I think it is a bug with bluetooth, not with airplane mode but I don't know how to solve the problem, it is really frustating.
Just for information, i have a galaxy s21 and a galaxy watch 4 46mm black both with the last update installed.