Procedure Issue with block detection

I have been having an issue to update a mobs coords to alter the blocks around it, not found a fix for it but found a work around, summoning a new custom mob that then triggers the procedure on initial spawn and then despawning itself.

This somewhat works  but now the issues are that it sometimes won't effect blocks and seems to almost always effect a corner block ( only the 4 directly next to the mob are currently programmed.) Obviously this is not ideal anyway but it also means it's spawning melon blocks without breaking the melon block so it is just spawning melons forever.

1. Spawning the Custom Mob: https://i.imgur.com/v6wRfG3.png
2. It is on Initial Spawn and only that: https://i.imgur.com/fFRTBTm.png

3. The actual procedure to alter blocks/spawn items: https://i.imgur.com/rft1VVC.png

All I can think of is the custom mob is having a dodgy spawn placement? Any advice or answers would be more than appreciated.