Thanks Marvin. We have now deployed FMC for the FirePOWER module, so we no longer need ASDM for that - therefore, we have now to downgraded to ASDM 7.6(2)150 so access rules all display OK again.

This still seems to be a problem with ASDM 7.7(1)150 released on the 9th March 2017. It'll usually display the source IP in the user/group column - and if you click it, it'll change the value to "any" or to nothing or blank out part of what was there...