A single tile won't load (Server error 500)

[verdy-p]

http://tasks.hotosm.org/project/3537#task/143
Gives HTTP 500 Server error, when loading tile data with XHR request to
http://tasks.hotosm.org/project/3537/task/143
But gives HTTP error 404 Not found, when trying it from a standard web browser.

The next tile to the right (145 instead of 143, same size) has no such error.

Signaled in
https://hotosm.slack.com/messages/C4MMB6PD4/

[verdy-p]

Apparently this occured randomly in several projects but these were lot filed here.

The current workaround is to use a nearby tile which is working. But the affected tile will not be subdividable with the UI (not even with the project admin privilege)

Editing/saving again the project does not solve the problem on these isolated tiles if this is caused by some caching issue on the server.

[verdy-p]

Some problem here (single tile that won't load because of HTTP 500 server error)
http://tasks.hotosm.org/project/3546#task/717