ST1300 rear brake locking,

[kappy5003]

Hi
Haven't been here for a while.
Been busy surviving.
An Old mate of mine has a 2006 St 1300 with approx. 90K.
For some time now he's had a issue with the rear brake locking to the point of being unrideable.
Each time after about 10 minutes, the brake releases enough to to ride home not using rear brake only using the hand brake minimally.
The bike has been in a Honda shop for several weeks and they are still scratching their heads, and it appears no sign of any solution in the near future.
The bill is around $2000 and climbing with talk of modulators in the area of $2000 each.
Has anyone experienced this on ST 1300.
Old mate is at the end of his rope and considering dumping her.
TIA

[Biggles]

Sorry to hear the expense he's been through.  It's a new issue to me, but suggests the brake linkage system.
Try a search on the USA site- there are a lot more answers there than here.  ST1300 brakes rank very high on the Tag Cloud there.
https://www.st-owners.com/forums/

The brake system simulation is fascinating.  Try moving the variables...
https://mjc-506.github.io/st1300braketoy/