Apologies for the delay. Attached is an example file. There are some example deactivated fillets which all produce errors depending on the size of the fillet and/or the propagation method. If you could suggest the mechanisms behind some of these errors I would be very grateful.
I've read the documentation, but still frequently come across errors while filleting, I was hoping there might be good practices that I've been missing!
Are you trying to Fillet across a part that has been split with a join?. If you are then you probably need to federate the joinf so that it acts like one element. Variable fillets sometimes stop at join boundaries.
What surfaces you need to hold. You are trying to have two variable fillets touching each other.
The second fillet operation is going to get confused, it is trying to hold a size and tangency at the same time and your flat runs out.
Either a smaller fillet so you always have a small flat left, or a tri-tangent.
The tri-tangent will remove the flat completely.
See attached images.
One image has tri-tangent fillets, the other has variable fillets with reduced size (0.9>1.5>1.5>0.9)