I did not replicate your issue.
I assume it might be related to the fact that previous firmware updates were performed with keeping the configuration settings from those versions.
The easiest solution, I would like you to try, is to perform your device's reset to factory default settings and see if that resolves it.
Alternatively, you can try making configuration changes by logging to your device via CLI/SSH with the following commands:
- uci set wireless.radio0.channel='<channel_number>'
- Replace <channel_number> with the number of the channel you want to set
- uci commit
- /sbin/wifi reload