Rendering of custom maps broken?

Instead of the original Garmin maps with rather rare details, I like the customized OSM maps from

But the FR955 seems to have huge problems to render them correctly, other than e.g. the older FR945 or even the Fenix 7 which render the maps in great details.

Left: FR955, right: FR945 

same Map loaded into the GARMIN folder.

The FR955 seems to fail with rendering any roads or footpathes at all.

Also names are rare...