[BUG] bluetooth HSP/HFP does not work with autodetect_mtu=1

[ghjp]

Describe the bug
When the feature autodetect_mtu is switched on (the default setting) no sound can be heared in a bluetooth headset. I have tested this with 5 different BT headsets. After a while the connection to the headset is dropped. If I switch off the autodetect_mtu feature every thing works as expected

To Reproduce
Connect a bluetooth headset and switch pulseaudio card profile to HSP/HFP. Now play music and set the output to the headset.

Expected behavior
Sound/music can be heared in the headset.

Environment (please complete the following information):

• Distribution [e.g. Ubuntu, Fedora, Arch ...]: Debian 10 Buster
• Pulseaudio Version [e.g. v12.2]: 13.0
• Bluetooth Version: 5.54
• Installing via [e.g. manually compiled, precompiled package from xxx, ...] package manager

Pulseaudio logs:
(set log-level to 4 in /etc/pulse/daemon.conf)

avinfo of device:
(guide: #31 (comment))

Additional context
Before the autodetect_mtu feature was added the system behaved as expected.

[stale]

This issue has been automatically marked as stale because it has not had recent activity. It will be closed if no further activity occurs. Thank you for your contributions.

[ghjp]

This bug is still present!

[EHfive]

This project has been deprecated. #154

There will be no bug fixing commits anymore.