Mine was a sticky mechanism in the rear gate. Opened up from the inside and lubed all I could get to. Has not proven to be fully cured but better. I expect another door or two is slow reacting causing the issue.

Cheers, Charlie
If It ain't broke, Modify it!
87 Montero turbo Converted back in Spring1989
95 Montero SR 3.8 DOHC Only one?
93 Pajero 3 door 6G75 Mivec with paddle shifted 5 speed
Then a Gen2 SR with full coil independent suspension.