Printer hiccups with new RAX30 router

Hi. My old router died recently, so I bought a new one. It's an RAX30, firmware version 1.13.102_2. It works great, but I have a strange problem. Once each week, on Friday about 5:00 or 6:00 pm, the printer prints five pages of gobbledy-guk that looks something like this.

*♥userpostgresicctxbasepostgres

(New Page)

OPTIONS rtsp://192.168.1.5/ RTSP/1.0

CSeq:  1

(2 more pages ...)

╘ SMBr↑C╚▖ ▦😊PC NETWORK PROGRAM 1.0😊MICROSOFT NETWORKS 1.03😊MICROSOFT NETWORKS 3

I'd like to know how to prevent this. The printer is an HP Laserjet m1522nf MFP connected to the router with an ethernet cable and assigned to IP address 192.168.1.5. Most of the time I'm running a Gentoo Linux system compiled from (mostly) C and C++ source code. The problem started a few days after I installed the RAX30, so the router must be causing it. I don't use Microsoft Windows, except once in a  great while.

What else? I do see these lines, or something very similar, in the router's log file every Friday.

Any help would be greatly appreciated. Thanks!