You should do the heat shrink joints away from the flex point, the flex will now be concentrated at the end of the heat shrinks.
Lengthen the wires and keep the joints in an accessible spot, this may be under the roof liner.
You probably can do this without cutting the rubber boot, replace the roof fabric at the same time if needed.
This is not a quick fix if done properly.
I did a more detailed post but somehow it got erased, I could not be bothered to do it again but the basics are here.