Bug caused it, after a solution.
A few times now the game has 'failed' to load a chunk, normally part of the base/home and I end up rebuilding..
The game replaces the failed chunk with what was there by default.
Sometimes its just scenery, but in this last case its the original inside of the building, taking away all my storage boxes and other interior changes I made.
I have noticed however that a pair of files get created in the Region folder in the saves, in this case they are
error_backup_45_41.comp.bak
error_backup_45_41.uncomp.bak
If there is anyway to restore the chunks then I would be grateful, I do have a copy of the files from 3 hours earlier, so not end of world but I would prefer to not of lost it.
Btw log data...
2021-01-20T22:26:46 11093.102 ERR EXCEPTION: In load chunk (chunkX=45 chunkZ=41)
2021-01-20T22:26:46 11093.102 EXC Attempted to read past the end of the stream.
EndOfStreamException: Attempted to read past the end of the stream.
at PooledBinaryReader.ReadByte () [0x00008] in <e9521218400243e9ac8c145545b586cf>:0
at PooledBinaryReader.ReadBoolean () [0x00000] in <e9521218400243e9ac8c145545b586cf>:0
at ItemValue.Read (System.IO.BinaryReader _br) [0x000dc] in <e9521218400243e9ac8c145545b586cf>:0
at ItemValue.Read (System.IO.BinaryReader _br) [0x00098] in <e9521218400243e9ac8c145545b586cf>:0
at ItemValue.Read (System.IO.BinaryReader _br) [0x00098] in <e9521218400243e9ac8c145545b586cf>:0
at ItemValue.Read (System.IO.BinaryReader _br) [0x00098] in <e9521218400243e9ac8c145545b586cf>:0
at ItemValue.Read (System.IO.BinaryReader _br) [0x000f1] in <e9521218400243e9ac8c145545b586cf>:0
at ItemStack.Read (System.IO.BinaryReader _br) [0x00015] in <e9521218400243e9ac8c145545b586cf>:0
at TileEntityWorkstation.readItemStackArray (System.IO.BinaryReader _br, ItemStack[]& stack) [0x00026] in <e9521218400243e9ac8c145545b586cf>:0
at TileEntityWorkstation.read (PooledBinaryReader _br, TileEntity+StreamModeRead _eStreamMode) [0x0003b] in <e9521218400243e9ac8c145545b586cf>:0
at Chunk.read (PooledBinaryReader _br, System.UInt32 _version, System.Boolean _bNetworkRead) [0x00562] in <e9521218400243e9ac8c145545b586cf>:0
at Chunk.load (PooledBinaryReader stream, System.UInt32 _version) [0x00000] in <e9521218400243e9ac8c145545b586cf>:0
at RegionFileManager.loadChunk (System.String _dir, System.Int64 _key) [0x0012d] in <e9521218400243e9ac8c145545b586cf>:0