Business Visa - B1

Hello, I have been going through this forum for a while now. I recently had the B1 Visa interview and had to face the rejection even though I had Previous L1 B Visa approved and i stayed in US back in 2014-15. I have also traveled to other Countries( Schengen and Ireland) on Business Visa from same company. Here is how my Interview went :

VO: Why you are travelling to US?
ME: I am travelling to attend Business Discussions and Meetings with Business Stakeholders.
VO: People coming in meetings are of same/parent company:
ME: Yes we have internal meetings where various YYYY location Representative are joining this.
VO: Designation?
ME: Senior Consultant
VO: Looking at all the visas I had in past at my passport. What is Exp with YYYY company?
ME- 7 years now.
VO: What is package?
ME- YYYY LPA. I have good package with respect to Industry standards.
VO: Looking at her computer monitor , why have you overstayed in Ireland during your business visit.
ME- I never did that mam.
VO: You did, that is what it shows , give me the reason:
ME- I never did that, if that would have been the case I would have got the red stamp on my passport. I can show my passport with all the exit stamps within time limits.
VO: I am not asking if Immigration allowed or not or they gave permissions. I am asking reason why you overstayed.
ME: Since I never did this overstay I have no reason to give.
VO: How long you were staying with Ireland in business visits.
ME: 2 to 3 Weeks.
VO: Continuously typing something on screen and said visa not approved.

As I came out I was really shocked to learn that I have overstayed and that too I have never been caught:). I was more concerned with my Travel History rather than B1 Visa. I recently had Schengen Business Visit Last month without any issue nobody mentioned about overstay in Ireland.

Anyways, with the above conversation I was sure my rejection reason was overstay which I never did. So post my interview I reached out to Ireland Immigration office to understand what is the issue here did I ever Overstayed with you guys. If yes, then send me the duration so I can show the proofs. I have been on 2-3 Weeks Business Visits in Ireland for 5 times but never seen any issue.

I have been mentioned by Immigration office that you never overstayed with us. In all your business visits your history is absolutely clean. It depends on USA Visa Authority why they are considering if you overstayed with us.

I am really not sure now what should be done in this case. Is my understanding correct with the above conversation that rejection was due to overstay issue which VO mentioned? As I have the email from embassy mentioning that you never overstayed so shall I re apply with the proof?

Please advise!!