I've experienced this frustrating issue on two different Teams desk phones from different manufacturers over the past few months as we've been piloting some new phones to replace our old Polycom VVX series devices.
Steps to reproduce:
Answer or place call on Teams desk phone
Place call on hold
Hang up handset
Call is terminated as handset is placed
This also happens if the user hangs up the handset while in the transfer call menu. The only instance this doesn't happen is if the call is parked.
The expected behavior is that the call would continue to be on hold until the user picks the handset back up, presses the 'resume call' button, or the transfer is complete.
After opening a support ticket with Crestron and waiting weeks to hear anything back, they basically said "Yes, what you describe is what happens. Can we help you with anything else before we close this ticket?".
So I'm back here, trying to get Microsoft's attention on the issue.