Bummer. Are they going with stainless steel this time around or same product? If same, I'd take that vehicle thru an underwash more often.

 

Just had the same issue on my 2015. My shop capped off the rear lines so I could have the front working at least.

See if they dealer is willing to do that for you. Front AC does just fine to cool the car down, and is better than no AC while you wait for a backorder...

 

4th generation Highlander seems to have a faulty freon line to the rear condenser that needs to be a Toyota recall.
My 2020 line failed "due to corrosion" at 16,000 miles. There are only a few points of light surface rust on some of the other body hardware under the splash panels, no significant corrosion on any other lines.
Another thread here reported the same and that even Toyota was out of stock on the lines (due to demand?).
Dealer repair cost was $703 for line replacement & recharge.

 

Just had my rear air con. lines capped, because of corrosion. only the front A/C is working now, dealership wanted 6000 for new rear air con. lines (2) and 2000. to install. Got the lines capped and front recharged for $200.00 !