I have the same issue for some keys. It works for every key except Numpad#3, which I cannot store using Ctrl/Numpad#3.
I usually assign the numpad#3 key to "copilot view", there's no way I can save it in the CL650, I have to resort to assigning it to "sit in copilot seat", but it's not my preferred viewpoint.
Of course I triple-checked there was no assignment conflict, could not find any...
Strangely enough it works for all other viewpoints I have assigned (#5 to pilot view, #9 to overhead, #2 to pedestal, and so on), they all work and get saved as wanted, the only one I cannot save is the copilot view