Chunks Missing around my spawn

I have just loaded up my Survival Island world to find Chunks have been missing around the island / the spawn point for the world. The chunks don't contain the block data from last time I loaded up the world which was over 2 weeks ago, probably before 1.19.71  The world is about 9 months old

I can walk through these missing chunks and fall through them into the void, water doesn't seem to react to the missing blocks though. Very odd

I hope the attached images help explain these missing chunks.

Thank you.

Kind regards.

Sam