Downstairs sink gurgles when upstairs washing machine drains
When my upstairs washing machine drains the downstairs kitchen sink gurgles. The washing machine is a combination washer/dryer with the dryer being a non-vented type. Both the washing machine and the dryer water reservoir outlet tubes are connected to a 40mm(could also be a 32mm, not sure just eyeballed it) standpipe that disappears into the upstairs floor.
I have no idea how the upstairs drain pipe connects to the rest of the drain system. The place is a rental and the landlord put in the washing machine drain pipe before I moved in. Doubt that my landlord hired a pro to do the plumbing upstairs.
Is this a partial clog? If so, is it more likely to be between the washing machine and the kitchen sink or is it downstream of the kitchen sink? Or is it not a clog but just my pipes not being large enough for the volume of water draining from upstairs.
Extra info:
I'm in the Netherlands and the house is quite old (1910-1920).
It's a rental so I don't exactly know the layout of the pipes and ripping out the floor/walls isn't really an option.
Spouse uses a lot of detergent/softener and the washing machine gets used a lot.
The upstairs washer is located almost above the kitchen and is the only plumbing stuff I have upstairs.
There are no odors and everything drains properly, kitchen sink does not gurgle when I flush the toilet or drain the bathtub.
I have most hand tools a plumber has in his/her toolbox. I also have a drain snake and an endoscopic waterproof camera (but it's not very long, only two meter).
How do I tackle this gurgling issue?