The RepairCare resin used to repair these corner joints at Essex House does not shrink.
Then why have the cracks opened up since they originally joined ? There are several possibilities of which the two most likely are
(1) The wood has warped or shrunken since installation due to changes in moisture levels since the wood was placed in situ. These new sills were exposed to rain and sunshine for many months before being painted or
(2) The RepairCare resin was placed on bare wood without first applying RepairCare DRYFIX to the cut surfaces prior to joining. This means that the resin failed to cling to the wood as originally intended.
Possibly both reasons have contributed to the problem, which is now common on many of the newly repaired windows.