Well, if taken at face value, and, as you affirm, the Cllr is receiving personal financial reward as a consequence of a PC grant - then the PCs grant awarding process is flawed.
I would maintain that the 2 parts - a Cllrs DPI and a grant of public money to an individuals personal advantage - are mutually exclusive.
If (IF) there is a DPI which is not being declared then there is a breach. If the is a non disclosable interest refer to your standing orders. If there is neither, the question doesn’t exist.
If you are saying YOU believe there absolutely is a DPI, then refer to MO.