For the E4 engine it sounds like the door itself isn't rigged correctly, they pop open on landing normally if they're not rigged not through blow-out pressure.
In Chap 78 after the rigging of the C-duct latches there is a page on rigging the doors, it also mentions that the fwd door should always be closed before the aft to ensure they're correctly latched.
If that's all done correctly then you should consider what the last poster says and check for broken ducts or air leaks, again there's only a small mention of this in Chap 78 as follows
The function of the forward and rear latch access doors is to make
the air flow over the latches smooth. The latch access doors also
allow for access to the thrust reverser latches. Also, the rear
latch access door operates as a pressure relief door for the zone 3
air. This function would be used if a duct breaks open or if air
leaks occur.
Zone 3 is cooling air for the turbine case, the outlet for this is where the aft c-duct latch panel is! Chap 75-21 has some good basic info on Zone 3 air and the px relief too.
Hope this helps.