'Start Recording Output' function broken in 5.4?

Hi there! I’m building a prototype that requires the ‘Start Recording Output’ and ‘Finish Recording Output’ functions. This seems to work fine in 5.3, however I cannot seem to record more than a microsecond in 5.4.

I have made a lot of progress in 5.4 so would rather not start again in 5.3 - is there a way to fix this in latest? Has anyone else encountered this issue? Thanks!