Thanks for the reply Jason.
As luck would have it - it hasn't crashed since! I've reverted the recordings to mp3 as well and both instances are running without a hitch. will watch and wait though just in case.
One thing I did notice after some scheduled maintenance this weekend is that after a restart only once instance will run automatically, I have to start the second instance by hand even though it is set to run by itself. No big issue, I could always script this to delay start as it's probably the first instance confusing things. Ideally if they could start as services it would be ideal then after a windows restart I wouldn't have to worry.
Anyhow, thanks as always for your excellent software, keep up the good work and I will arrange to drop a donation in to say thanks!
It would be good to see the error that is occurring with the MP3 recording. The WAV recording records at 44100Hz Stereo and this cannot be changed. Naturally, it has a large footprint due to it being uncompressed. If you have some scripting ability you could use something like ffmpeg to compress the WAV files to MP3 after the recording has completed. Here's an example: https://stackoverflow.com/a/12952172/762687