By ‘Reswitching” I suspect that you mean the loss of supply to the bus feeding the drive either due to grid failure of switching from one supply to another and your expectation is that the drive will ride through this event then re-establish speed/flow when the power is restored. This is possible and the principle is known as” kinetic buffering”. It involves using the momentum stored in the driven system to keep the drive control alive whilst there is no incoming feed and reducing speed in a controlled manner to avoid overloads but its success depends on a number of variables including length of supply outage and inertia of the driven system. First of all check that your VFD support “Kinetic buffering”, not all do, and that it is correctly programmed to make use of the feature
I hope that this answers your question but, if not, and you want concise answers you need to be specific in your question indicating the situation and your desired outcome so that people do not have to try to guess what you mean.