IMHO first and easiest check tool is ping for ensuring if the device really lost connection. If it's alive it would mean that its most probably application issue.
I don't know what application (or what kind) is that and don't know where are devs looking and what kind of log level is set but maybe it's not error. or error they are "catching" ATM.
I hope that they don't expect uninterrupted connection because there is no such thing in wireless environment and application must expect small network outages and handle them properly (lower timeouts, more retries etc)
Maybe it's server, session, etc issue. Was different Android device tested or maybe Zebras on different WLAN infrastructure? For example take two APs with same ssid but with small signal "hole" between and install app on any other android smartphone and try to move between them how it would react. Or just one AP and move away and back while working in app to see what it does and if devs would see errors.
that are first thing that came to my mind but appropriate troubleshooting methods should be used at first of course
And also if default android debug logs are not providing informatins devs are looking for they should implement what they want directly to the app. Because IMHO if app is stucked devs should see it in logs so they can tell you (and also user notice in app) - server/database unreachable or so.