We had this problem intermittently around a year ago but it wasn't just limited to iPads - we experienced difficulty with iPhones, specifically 5si & SE models.
Turned out to be an Apple iOs issue in the long run.
Might not be the resolution to your specific issue but another avenue worth exploring.
IT Systems Engineer, XCWT & XCWP
SEC | Scottish Event Campus | Glasgow G3 8YW | UK