Switching to external speaker does not work if another call is ringing in during a phone call

[vanous]

Thank you for all the work on SimpleMobileTools!

Sometimes, the external speaker button in an ongoing phone call stops working - call cannot be switched to the external/loud speaker anymore. This is a bit harder to replicate but it seems that this issue can happen in the following sequence of events:

• receive and answer a call (A)
• remain in "normal" mic/handset speaker mode (so no external speaker)
• another person tries to call (B) you, but gives up - call (B) is not accepted
• then you try to switch the still ongoing call (A) to a speaker but it does not work

Android 11, Simple Dialer version 5.12.0