ABS problem?

[Sparetyre]

Hello, this is my first post to the forum. I have a 2005 Yaris Mk1 which has over the past couple of years developed an issue with ABS. No warning lights come on but if I brake at very low speed (6mph or less) it's as if the ABS system thinks I'm in a skid and eases off the pressure on the brakes. I hear a clicking noise as this happens. This happens less frequently if I brake heavily but I don't generally drive on my brakes so don't often apply lots of pressure to the pedal. This doesn't seem to be an issue for MOT certificates and I've asked my repair garage (not a Toyota specialist but they're v good) to have a look. They can't find any problems with ABS sensors and have said it's nothing to be worried about. However, I'd like to get it sorted if possible in case it develops. I'd be grateful for any advice on what the problem might be - a bit of internet searching has brought up the issue of reluctor ring problems.

Many thanks,

Sparetyre