This is the nature of Z-wave repair. If some devices are having communication problems, or the network is very busy, a network wide repair could cause increased instability in the network. In general, network wide repair should not be necessary and is generally not recommended unless you have relocated the hub or made significant changes to the network (e.g. adding, removing, or moving many mains-powered devices).
Here are a few post from Hubitat Staff that may help you understand what repair is doing (and perhaps when it is and isn't a good idea to use it):
