LaserJet Pro MFP M148fdw won't scan using SANE on Raspbian Stretch

I've installed HPLIP 3.18.12 (with the Debian patch to disable libImageProcessor.so) on a Raspberry Pi 3 Model B running Raspbian Stretch to act as a print server in a small network. Printing works fine so far.

However, when trying to set up my LaserJet Pro MFP M148fdw for scanning using SANE, xsane spits out the error message: "Error opening device `hpaio:/usb/HP_LaserJet_Pro_M148f-M149f?serial=VNL4K00226': Error during device I/O."

hp-check -b runs without indicating any errors, also the output looks perfectly fine.

The output in /var/log/syslog looks like it could provide a clue, something is going awry in the last 6 lines of output:
Jan 4 22:24:58 raspberrypi hp-check: io/hpmud/musb.c 389: Active kernel driver on interface=0 ret=0
Jan 4 22:24:58 raspberrypi hp-check: io/hpmud/musb.c 535: claimed 7/1/2 interface
Jan 4 22:24:58 raspberrypi hp-check: io/hpmud/musb.c 781: read actual device_id successfully fd=1 len=304
Jan 4 22:24:58 raspberrypi hp-check: io/hpmud/musb.c 561: released 7/1/2 interface
Jan 4 22:24:58 raspberrypi hp-check: io/hpmud/musb.c 2189: [3503] hpmud_make_usb_uri() bus=001 dev=007
Jan 4 22:24:59 raspberrypi hp-check: io/hpmud/musb.c 2287: hpmud_make_usb_uri() uri=hp:/usb/HP_LaserJet_Pro_M148f-M149f?serial=VNL4K00226 bytes_read=53
Jan 4 22:27:40 raspberrypi systemd[1]: Started Scanner Service ([::1]:53400).
Jan 4 22:27:40 raspberrypi saned[3766]: saned (AF-indep+IPv6+systemd) from sane-backends 1.0.25 starting up
Jan 4 22:27:40 raspberrypi saned[3766]: check_host: access by remote host: ::1
Jan 4 22:27:40 raspberrypi saned[3766]: init: access granted to saned-user@::1
Jan 4 22:27:50 raspberrypi saned[3766]: io/hpmud/musb.c 427: Found interface conf=0, iface=0, altset=0, index=1
Jan 4 22:27:50 raspberrypi saned[3766]: io/hpmud/musb.c 389: Active kernel driver on interface=0 ret=0
Jan 4 22:27:50 raspberrypi saned[3766]: io/hpmud/musb.c 535: claimed 7/1/2 interface
Jan 4 22:27:50 raspberrypi saned[3766]: io/hpmud/musb.c 781: read actual device_id successfully fd=1 len=304
Jan 4 22:27:50 raspberrypi saned[3766]: io/hpmud/musb.c 561: released 7/1/2 interface
Jan 4 22:27:50 raspberrypi saned[3766]: io/hpmud/hpmud.c 683: invalid channel_open state
Jan 4 22:27:50 raspberrypi saned[3766]: http.c 300: unable to open HP-SOAP-SCAN channel
Jan 4 22:27:50 raspberrypi saned[3766]: bb_soapht.c 661: unable to open http connection hp:/usb/HP_LaserJet_Pro_M148f-M149f?serial=VNL4K00226
Jan 4 22:27:50 raspberrypi saned[3766]: bb_soapht.c 793: unable to get_scanner_elements: uri=hp:/usb/HP_LaserJet_Pro_M148f-M149f?serial=VNL4K00226
Jan 4 22:27:51 raspberrypi saned[3766]: saned exiting

Obviously the interface closes down before the connection between computer and scanner can be established. Can anybody provide me with a clue how to remedy the situation so (x)sane can communicate freely with the external device?

According to the compatibility table in https://developers.hp.com/hp-linux-imaging-and-printing/supported_devices/, the device should be fully supported by HPLIP.

Kind regards,

Amy