When typing on the on screen keyboard, you can choose to hear a clicking sound as you type each letter.
As a VoiceOver user, these sounds are intermittently disappearing. You may hear them for the first few letters or words of a message for example, and then find they stop.
Ensure Sounds are switched on in Settings > Sounds & Haptics > Keyboard Feedback.
Switch on VoiceOver.
Go to any text field and start typing, I primarily use the the Direct Touch Typing method.
Some of the time I will hear the keyboard clicks, and some of the time I will not.
Often they are there to begin with but soon disappear.
I believe it is VoiceOver related because I have tested with VoiceOver switched off and the sounds seem to remain.
None