2017 Lexmoto XTRS part identification

Hi there, I have an issue with my other halfs XTRS. Being laid up over winter, gone to use it again in the better weather, and the rear brake is binding, enough that it'll overheat and seize. The rear wheel will move initially, and the brake pedal works, but the brakes just aren't coming off enough to stop it binding. Ive stripped down the rear brake, pushed the pots out and put some copper grease on them around the seals, cleaned it all up etc and put it back together but still no joy. Other threads elsewhere that Ive found with similar issues suggest maybe a sticky return valve. The bike itself has only done about 350 miles so far, so still pretty new.

The calipers have a yellow/gold coloured cylinder on each one, that I have no idea what it does, and doesn't show up in any part list either, other than if you buy a complete rear breaking system, it has a sticker saying ABS on it, but I highly doubt a cheap bike like this has ABS.

Can anyone help me identify the part in question pls (the photo actually shows the front caliper and its "part", although the rear one is identical)

Thanks in advance

Attachment 20101

Give me please three first letters of vin number. I will look in Poland.

Change the brake fluid to name brake. U NEVER know what's inside the stock...
Cheaply ABS = http://www.chinariders.net/showthrea...314#post213314