I have checked. The problem is still present in HPLIP 3.9.6. The output files still contain the non-working sequence "<ESC>&l14H<ESC>&l0M" (using the HPIJS driver).
I tried it also with the hpcups driver, but I needed to fix the hpcups.drv file so that the CD Tray gets available in the PPD (patch attached). Also here the wrong "<ESC>&l14H<ESC>&l0M" gets inserted.
I have checked. The problem is still present in HPLIP 3.9.6. The output files still contain the non-working sequence "<ESC>& l14H<ESC> &l0M" (using the HPIJS driver).
I tried it also with the hpcups driver, but I needed to fix the hpcups.drv file so that the CD Tray gets available in the PPD (patch attached). Also here the wrong "<ESC>& l14H<ESC> &l0M" gets inserted.