Frequent grey tiles viewing OpenTopomap

[haylingchrist]

I frequently see many grey tiles using OpenTopomap even when the relevant tiles are obviously in the cache.

E.g. when viewing the map, select 'settings' then return to the map. Sometimes its a complete grey screen.

Or zoom out, tiles go grey, return to the original zoom - tiles remain grey.

Or when zooming in initially the old tile is displayed enlarged but then it goes grey while (I guess) waiting for the higher zoom tile to download from the server.
Since the OpenTopomap server is often slow this can take multiple seconds or even minutes.

This isn't survivable when navigating a motor vehicle and I don't find any of the other online world maps clear enough for the job.