Created attachment 230211
Test series with different printer drivers, files and programs
I can reproduce this bug here. This looks similar to bug #307267. The user who reported this bug already opened an hplip bug as he verified this problem with Xubuntu. So this does not look like a Gentoo specific bug.
I did a test series with your test file and the one from bug #307267. Like you said this only happens with hpcups, but the results with for the two test files are different like you see in the attached file.
Created attachment 230211
Test series with different printer drivers, files and programs
I can reproduce this bug here. This looks similar to bug #307267. The user who reported this bug already opened an hplip bug as he verified this problem with Xubuntu. So this does not look like a Gentoo specific bug.
I did a test series with your test file and the one from bug #307267. Like you said this only happens with hpcups, but the results with for the two test files are different like you see in the attached file.