How to get rid of Patching due to Ronseal Knott Block getting on the wall

The problem is that the Ronseal Knot Block is still sealing the surface, so the paint is drying differently over those areas and causing the flashing. I'd avoid sanding endlessly. Sand the affected areas enough to remove any obvious ridges, then prime the whole wall with a suitable adhesion/stain-blocking primer, rather than just spot-priming with Dulux Aqua UniPrimer. Once fully dry, lightly sand the primer and apply your chosen wall paint. If the Ronseal has left a very hard, glossy surface, you may need a stronger bonding primer designed for glossy/non-porous surfaces. Also make sure the existing wall is clean and dust-free before priming. The key is to get one uniform sealed surface across the whole wall before applying the final coats; otherwise the repaired areas can continue to show through as patches