Renault Clio MK2 signals left whether I indicate left or right after hazard warning switch played with

Timeline

- Took car for MOT last week,
- Get phone call that Hazard Warning Switch isn't working - charged £x for diagnostics with possible extra charges if, say, new part needed.
- Phone call two days later, car ready to pick up. No extra charge. Receptionist say they just gave everything a good clean and it works.
- Drove home (~three miles). Didn't notice anything odd.
- Went for longer drive today. If I indicate left or right the left indicator button illuminates in the dashboard and the lead indicator light flashes on the car (at least on the front end, haven't checked rear yet).
- Pressing the hazard switch illuminates both indicators on dashboard and on at least front of car (see above).

I didn't notice anything odd when I drove home from the MOT but that doesn't mean there wasn't an issue - maybe I didn't take any right turns, or just didn't notice. It would be a strange coincidence if this issue was unrelated to the hazard switch being played with, but possible.

What should I do? I'm willing to put in a new hazard switch if it's not too big a job and would fix the issue. I can also go back to the garage. My worry with the latter is - if they can't fix the issue (or charge something prohibitive), would I be allowed to drive the car? I don't use it much but when I need it I need it and I'd rather go 10 or 11 months right signalling by hand then get a new car than get a new car right now, when the timing is a bit awkward.

To add something to the timeline - I had to reenter the radio code when I picked the car up - suggesting the garage disconnected the battery. In the past I've had dashboard issues after disconnected the battery, the issues generally went away after a while. This is perhaps a bit different because there's an issue with the actual indicator in addition to the dashboard, but the problem could actually be related to the ECU rather than the hazard switch.

Sounds like an earthing issue. Very common.

You'll likely have a corroded rear light connector, corroded earth from connector to chassis in the boot or a corroded bulb.

Check these first, if hazard switch turns on and off its not faulty.

hazard switches are very common on these, I always keep one in my toolbox. generally they fail and the hazards come on and stay on though.

As above rear light connectors are bad for causing earthing issues.

I've seen faulty BCM's cause the car to always just indicate left even when the indicator stalk is in the off position - usually disconnecting the battery for 20 seconds solves this for a few hours/days/months

Uch needs repair. Send it off to the company on ebay to get it sorted.