I use the word glitch because for some this would not be a problem.
The rear storage hatch on my 2000 Excella has a rubber seal that I'm certain keeps critters, dust etc. out pretty well.
But I have noticed on many like mine and including mine that outside chairs, tarps, cushions and all sorts of things used outside are stored in this area.
After camping for several days all sorts of critters attach themselves in all sorts of cracks, rods, poles etc.
When you repack your storage area then all these critters proceed to enter your home on wheels VIA under your bed.........
Spiders love round poles, especially black widows.........
This storage area should NOT be designed to go under the bed. It should be sealed off by putting a piece of 1/4 inch plywood easily done against the entry part under the bed.
Once this is done, it can be caulked with clear silicone or something to keep smaller critters out.
Another problem is all the dirt accumalated on the legs of all the chairs, tables etc. end up under your bed and eventually will end up in your bedroom or carpet from pulling stuff out from under your bed.
All outside things that have been in the rain and outside should be stored in a sealed area away from your living quarters.
This is a simple 1 hour fix, though it does cut down a little on under bed storage I would rather know my under bed is clean as the rest of my camper.
On the excella model like mine I have found 2 storage hatches that have open access to the inside, one in rear and one on street side that is open at top a bit and goes under my dinette seat.
The battery boxes are pretty well sealed to the outside.
The reason I am mentioning this is because I found a monster spider under my bed.