Crazy sounds on clicking a note

I am using MS4 using playback and get this insuperable problem whenever clicking a note on the score.
It happens on every single note.
It happens at whatever volume my my speakers are set to.
I attach a video of what happens.

Secondly, this problem is exacerbated when I start a playback on a place in the (choral) score where not all parts are singing. EG SA out of SATB. The playback is totally flawed i.e. jumpy and echoey and slow UNTIL a section in the score is reached where ALL parts are singing!
I can reproduce this at will; i.e it happens all the time. Unfortunately I can't seem to be able to send you a video of this because the file size is enormous. But imagine it as a continuation of what you see in the attached video.
MS 4 is much the worse for this happening and I revert to normal audio sometimes in order to compose effectively . Very disappointed.
I have done an Audiochecker on my sound system and all is in order. Running Windows 10.

Al this is on top of the general playback issues that I have with Muse Sounds - the surges on loud sections and the deafening overload on the speakers, NOT ONLY MINE but on other people's systems. I have had to limit the dynamics to mf to stop this happening. This is a real shame because the quality of the sound is so much better than MS3.