issues with R raster temporary files

Hello.

I am running into difficulties running some older scripts I produced in
2014 to handle raster data using the R package "raster".  I have the
feeling that some behavior has changed with an upgrade but don't
remember what version I was using when I wrote the scripts.  Can
somebody help me troubleshoot and solve this?

The general problem seems to be that R is not recognizing automatically
generated temporary files I run `removeTmpFiles(h=0)`, so I end up
with lots of large .grd files that stick around.  Having looked at the
source code for `removeTmpFiles` and `showTmpFiles` and also looked at
the files sticking around, I think the problem is that temporary files
are being generated without a prefix (i.e. the file name just starts
with the date), but I'm not sure why this is happening or how to fix it.

Any advice?

Thanks,
Alex