Unwanted font changes on feedback layers

Around two weeks ago I noticed that when I opened a Storyline 360 project I'd been working on, that the 'title' text on some of my feedback layers had changed from Effra to Helvetica. My feedback masters specify Effra as the font that should be used, the actual layers that the feedback masters are applied to used to display correctly using Effra, but since I updated Storyline they now display using Helvetica. Randomly some of the display sizes are changing too. Oddly, these issues don't affect all instances where the feedback masters are used.

I went through and fixed everything and I have worked with the file on and off over the last couple of weeks, without noticing any further issues.

I updated Storyline again this morning and it seems as though all of the same issues have returned. I'm struggling with this as the project I'm working on has been QC'd and is almost ready to go. Now I'm at the stage where I need to do another time-consuming sweep and hope I haven't missed anything. 

I'd be grateful if anyone could tell me why this is happening and if the updates to Storyline have caused the problem.

Thanks.