I'm using WinCompose 0.9.4 in Windows 10.0.18362.535, and since when I updated to this version sometimes it doesn't accept some combination; examples of not accepted combinations are:

<Multi_key> <è> <è> : "È"
<Multi_key> <equal> <Right> <Right> : "⇒"
<Multi_key> <equal> <Right> <Up> : "⇗"
<Multi_key> <question> <question> : "[backtick]"

last one should give a backtick; instead of those, I get:

è
[moves right]
[moves up and right]
?

I'm not sure how to replicate this: it's not from system start, or at least not always, it seems it happens after a while the PC is on; if I restart WinCompose, it works fine again.

Edit: It just happened again, nothing changed since I restarted it; it seems after a while it has issue, and restarting it solves them for a bit. I literally used WinCompose to do a backtick, wrote four character, tried again to do a backtick, and I got ? instead.