'pending background load task' after Hololens hard-reset

[zantiu]

WLT was not longer working after I had to do a hard-reset of our Hololens 2. The WLT diagnostics HUD showed 'pending background load task' in red. It also showed 'current fragment: invalid'.

Hard reset executed as described here: https://docs.microsoft.com/en-us/hololens/hololens-recovery

The reason I did a hard reset was because when testing with our application (including WLT) the connectivity to an external server was not stable. The connectivity issues seemed to come from the Hololens since the connection to the device manager was also very sporadic. A soft reset did not fix the issue.

Maybe something went wrong during the saving of the WLT data, and then it could not be loaded again.

The issue only went away after a complete delete and reinstall of the app.

Possible solutions: (in order of preference)

• Avoid this issue. (Not sure if possible)
• Automatic recovery when this issue happens (for example discard all saved anchors and start from scratch)
• Give a message to the application that can then prompt the user that the app needs to be completely reinstalled.

[fast-slow-still]

Thanks for the detailed writeup! That's very helpful!

This is going to be a tricky one. The load task is run asynchronously, so it is not uncommon for a couple of frames of update to be missed while the load progresses.

So the only way (that I can think of offhand) to tell the difference between a routine "skip update because pending load" versus a "something's gone wrong and this load will never finish" would be some variant of a timeout.

I very much dislike using a timeout, but there are times when that is the only hammer in your toolbox, as the saying goes.

I will see if I can repro this by manually corrupting the save file or something. Given a consistent repro, I might be able to find a more elegant fix.

Many thanks again for taking the time to report this!

[zantiu]

This happened again yesterday, again after a hard reset.