Analog sticks and D-pad stop working after phone locks (Samsung DeX)

I'm trying to play through Artemis/Moonlight on my Samsung S25 using Samsung DeX.

Everything works perfectly at first, but as soon as the phone locks or the screen turns off, the analog sticks and the D-pad stop responding. The buttons still work normally.

If I unlock the phone again, the sticks start working again.

Has anyone else experienced this or found a workaround? From what I've read, this seems to have started after an update several months ago, but I haven't seen any official fix yet.