I am a developer and have worked at this company 4~5 years by now.
We have been practicing scrum for about 2 years.

I think, I have been worked well with QAs.
I believe QAs/developers/technical writers are all one team.
We are also actively hiring new team members.
As a legacy member of the team, I have faced to assist new member(including developers and testers) with my business knowledge.

We work on 2 weeks base scrum.
I usually deliver my user story completely by the first date of second week and do some qa build with partial functionality of my user story so that QA has a good idea about my implementation and flow.

Recently, I have met some QAs.
In first week, the QAs do not talk... In stand up meeting, they say they are developing test cases regardless I deliver the user story or not.
In second week, I do not have a single defect till Thursday afternoon and suddenly I have a major defect with several minor UI defect, which I delivered one week ago.
Or I have one or two minor defects on second week however major defects on Thursday afternoon or Friday morning.

This eventually make the story rolls over to the next sprint.
Major defect takes time to fix and more importantly it would trigger the regression test for the story... Even if I worked Thursday evening and fixed it, the testing will not finish.

And this happens multiple times with certain QAs.

As a same team member, I talked to the QAs if they could test major defect with higher priority... Rejected... Because I do not understand QA process..

So I asked roughly how many major test cases are covered so far in the stand up meeting on 2nd week Wednesday.. The response is I should not ask this to the QA in the stand up meeting...

What do I do?