Delamination?

1998 Lunar caravan floor laid in two sections meaning joint midway. The floor sinks(Spongy) by the saloon sink so joint parts, more prominent towards the front of the caravan.
I've read' don't drill near where the floor sections join' but not how far the holes should be from the floor joint only says space 20cm apart shown in a square and all hole in line not staggard. Any idea how far away holes should be from the join.
Many thanks for reading and responses.