No problem switching between Fiasp and NovRapid.
I have Fiasp in my pump with NovoRapid and Lantus as my back up insulins in case of pump failure. It doesn't happen often but I am fine switching.
You obviously switched one way recently and, if Fiasp had not worked for you, you would have switched back.
Given the cost of insulin and the state of the NHS finances, I am surprised you were not encouraged to use up your NovoRapid before switching. I was given strict instructions to do so when I switched the insulin I use in my pump.