We experienced a similar issue, we found the underlying cause to be the location services being set to always whilst using the Servicemax app. Try to set this too whilst using or never to resolve your issue until you hear back from support.
Thanks for the detail on Location Services.
I found our issue was related to the Session Auto Refresh button. We always had that to ON and when updated to 18.0.12, it defaulted to OFF. Setting it back to ON fixed it for the few users who had the issue. We've not had Location Services turned on for ServiceMax.
We are also having this issue. I created a case and mention that I figured out that turning ON the Auto Session Refresh option seemed to be a workaround. According to them, this should default to OFF so that the timeout will not affect the iPad but seems that on this latest release the settings are "reversed".
The default value of the "Session Auto Refresh" should be True/On.
It is found that, in 18.0.12 the default value is False/Off. A new build (18.0.13) with this fix will be made available shortly on Appstore.
Workaround to the problem till then, is to turn ON the "Session Auto Refresh" setting.