I am hitting this issue where Maplex labels on the map tile cache occasionally get 'exploded' in a irregular way. My cache is build on Azure (5xF64s machines with ArcGIS 10.6.1 on it). I noticed that the issue applies to all tiles that get to be generated by the same TaskStatus. But on the other hand tiles on the neighboring Task area are all labeled as they should without errors. The corruption seems to be spread in random places across the cached map which is very frustrating as i dont know what is the criteria for this. So basically i get some random spread of corrupted TaskStatus areas. No errors seen in logs though. All marked as 'Success' in TaskStatus...
On the left there is the content of the corrupted Task Status. Street names get 'exploded' all over in that area. But labels in tiles generated in the next TaskStatus area, to the right, look fine everywhere. The cyan line to the right of the screenshot indicates boundary between the two TaskStatus polygons that i pulled out after the tile caching process.
The issue applies to many types of labels. Could be place name, town name, street name, etc etc.
If I rerun the caching process the issue goes away. This does not seem to be data related, as re-caching resolves it. I cannot get this in a reproducible, consistent way though. I suspect it might be machine specific (caching on a 5x multimachine site, all reading config from the same fileshare location, all boxes the same though), but then I cant tell which box would that be really. I cannot just stop one box, as then I if one of the nodes is not present in the site then submitting the caching job crashes. I tried keeping only one CachingTool as 1=min=max (instance number) hoping to redistribute the load across all 5 machines, but again all rendered OK, so i guess all machines did what they should.
It feels that in some random situations the Maplex engine randomly splits the letters of the Label, but i cannot tell why. I dont think its missing font related as it does render, it just exploded.