Return to service issues are certainly not confined to the Max, or any particular aircraft type. None of them are trouble-free out of storage. There is already an AD on 737 NG engine bleed valves for example. My own airline has been reactivating aircraft the past few weeks and finding runs of odd (benign, no dispatch issues) failures. I have flown three different aircraft over Christmas with the same odd retractable landing light issue, for example. I have never before seen that defect in my previous 25 years on type.
BTW...That Air Canada IFSD was apparently called for by the fuel IMBAL. non-normal checklist which directs that action. ie: it was a discretionary shut down and not an engine malfunction per se. It is a feature of non-normal checklists that they can sometimes be triggered by faulty sensors which then lead to an action that reads as prudent and considered within the context of the checklist but which may not seem so wise on Monday morning.