Hi John,
The version of android is quite old, but that should not be a problem. Is it possible that there is an android 4.2 update available ? If so, might be worth upgrading to that to see if it fixes the issue.
The only issue I've ever encountered which is remotely similar to what you describe was on one particular type of device (I forget which) during testing. I found that tapping the screen and holding the finger down for more than 5 seconds on an unused part of the app display (i.e. the part at the bottom of the screen below all the buttons) caused the app to vanish without trace ! This turned out to be due to a bug in the android system "webview" component. Earlier and later versions of the component did not exhibit this issue, and no BridgePal user ever reported it. I was able to work around it with an update which is now incorporated in BridgePal Server. However, it doesn't sound exactly the same as the problem you describe, because I get the impression that on your devices the problem occurs immediately on tapping the screen. In any case, you say you are now using the latest version of all the BridgePal components.
I think the only way I could diagnose the problem, and even then I can't promise, is if you were able to loan me one of your SumVision tablets to test with. If I had the device and was able to reproduce the problem I might be able to tell something by extracting the internal system log that is maintained by android. If you want to pursue this, I can email you my address and you could post the tablet to me.
Do you know which version of the PC software components you were using a year ago when the SumVision tablets were working ? We have made quite a few software releases in the last year, and some of them have mutual dependencies. For example, if you were to regress to an earlier version of BridgePal Server you would also need to revert to an earlier version of BridgeScore.
John