As I was cleaning up the tracks for the season, isolated joiners broke down; this is likely because of the lack of tie support and of the damaged plastic of the isolated jointers (likely because of the UV).
The solution is to install PCB track ties that are typically used at the end of a module to ensure rails will not be damaged or dislocated. I purchased this on eBay:
I soldered the tracks on the PCB ties. One side of the isolated joiners was still in good shape. I moved them to connect the two tracks on each side, which helps with vertical and horizontal alignments:
As I was working on ties, I started adding missing ties in other areas. I bought those a while back:
Here's the before and after:
Looks good!