We have a problem that multi-session role switch to windows remote desktop by itself.

Our devices:
TSPlus system edition 3 users v11.30.5.18
1 PC(windows 10 pro) with 3 different account(Ex. uesrA, userB, userC)
2 tablets
We use PC as a server and allowing tablets to RDP(by jump desktop). Everything works fine so far until last week.
On PC(login with userA), It popup asking to allow the RDP connection when I try to connect from the tablet with userB. Then, after I accept, userA on PC is logoff immediately like a single session. So, we figure out until we found on TSPlus that multi-session role switch to windows remote desktop by itself.
Anyway, where can I find a log or how to know why it's happened?
Thank you,
Wawio