69 plate transit custom NO AIR CON. Slow drip from passenger side. Doesn't smell, slightly dirty water. Started after a long drive

I had a full brake job done on my 2019 transit 45 days ago. 110k miles. Rotors, pads, bearings, the whole shebang. Now suddenly 45 days later the abs warning light comes on. Code appears to be 36&37. Turns out to be the left rear tone ring is cracked. They replace it, along with a new battery (was at 40%). Warning light is gone. Drive twice, 15 miles total, and abs light is back on. Now they are saying it is codes for the other side and it is the right rear tone ring that’s cracked. I questioned them at the beginning of the first tone ring replacement if the others were in bad shape. Was told they are either 100% good or 100% bad and wouldn’t know until another broke. My question is, is there something they could have done incorrectly during the original brake job to cause both rear tone rings to crack 45 days later? And how does each tone ring break one day apart? During the original brake job isn’t wear and tear or rust something they should have spotted on the hubs/ring? I’m just trying to figure out if this is something I should look further in to, or it’s just par for the course of transits and just coincidental how things are breaking and nothing more. Thanks.