Nether portal checks are not working properly

java : latest

OS : Windows 10

Ram : 8 GB ddr4

Processor : i5

MC version : 1.14 java
Nether portal checks are not working properly... a nether portal is supposed to remember the destination portal if a mob/player passes through it for 15 second. in 1.14 this does not seem to be the case as i have a portal ready to teleport 50 mobs or so.. the server immediately crashes due to the enormous load.