Audio dropping in and out, whole tracks not playing while others play fine

Just finished my first project on PP. It was perfect, everything worked fine. Saved it, took a break for an hour, came back and BAM! First 2 music tracks don't play at all (I've checked mute buttons, turned solo on and off, checked that they're 'enabled') while the last 2 play just fine! Then my voice over drops out for a couple of secs here and there, the mute button comes on all by itself and cuts out half of a voice over section and then magically turns off again. There are no markers in place anywhere and I've cleared the 'audio type' in case it was that, but that didn't work either. It's only a 12 minute project but the first half is now stuffed. Could it be a bug?

This also happened yesterday where the music tracks stopped playing and the only work around was to replace them with new tracks which worked...until they didn't.

I'm working on an Acer E15 laptop i7 8G ram, time for a new computer maybe?