If the FilletEdge is trying to make several fillets, and they are big, and their handles are linked, the FilletEdge fails - it makes very bad fillets. If the handles/fillets are big and not linked, they do not fail.
If the solid has several fillets and they were made in sequence (not at the same time), the Edit option of the FilletEdge command changes the last fillet only. There is no way to change the remaining fillets.
The Edit option of the FilletEdge command can change fillet radius and it can replace a blend and a chamfer with a fillet. The Edit option automatically selects all fillets (edges) and asks the user to left-click a fillet/edge to be changed. This is confusing because left-clicking the fillet/edge de-selects it.
I made fillets on both edges of a truncated cone before using the FilletEdge Edit and setting SetAll to zero. Rhino worked hard, displayed error message (Failure in trimming input.) and removed flat surfaces from the truncated cone.