Creation of Image Mosaic's from one or more *.asc files fail to create working wms

Current geoserver seems not to be able to create an Image Mosaice from one or more *.asc files

After first having some problems using my own asc files, see (search for 'shp index of mosaic of asc files fails to fill'):
https://sourceforge.net/p/geoserver/mailman/geoserver-devel/?viewmonth=201808
and
https://sourceforge.net/p/geoserver/mailman/geoserver-devel/?viewmonth=201809

I ended up to test just the precip30min.asc and precip30min.prj files that are provided as example asc files with Geoserver. All WMS requests to this store/layer fail.

To reproduce:

• copy precip30min.asc and precip30min.prj (from geoserver coverage data dir) to some dedicated directory

• create an Image Mosaic store for it

• note that a valid index.shp is being created (with in my case the valid bbox's)

• create a default layer from it

• the go to Layer Preview and try to view your layer as openlayers wms

• see the error that is viewable in attached image

I first had the impression that it had something todo with my data being nog epsg:4326 and some resampling was faulting. But as the above simplest test is not even working, I think there is more.

In the mailinglists are some stacktraces, plz let me know if needed here.

Happy to test/help/debug, or provide (other) data, please sent and email to richard@duif.net