So you are using mac host?
What firmware are you using? Only repetier-firmware sends wait by default. Marlin can do but is normally not configured to do so. CBD uses wait with different meaning.
M115
will show you used firmware.
For more information, log a print and check the point where it starts +/-100 lines to gasp what changed. Normally a wait means firmware has nothing to do and we continue sending so after that communication normally works well again. That is why it is used after all.