Whatsapp keeps deleting my contacts??

I added some contacts through whatsapp to then save to my phone, and it deleted them from both the app and my phone contacts. I then added them through my phones contacts app, and whatsapp...still deleted them?? I've tried messing with settings and everything but don't know how to fix this or even whats caused it. I dont HAVE many contacts currently but im still a bit concerned because i've almost lost a family members number due to this