Out of network claim reimbursements, deductible met date of processing and not date of service?

I’m trying to figure out an out of network reimbursement situation and I could use some help. I see a provider who does not take my insurance. Monetarily it’s not ideal and I’ve considered switching, but the progress I’ve made and continue to make compared to previous providers is 100% worth it so I consider it necessary. I pay in full at time of service and then at the end of each month my provider sends me a statement of dates of service, charges, codes, etc. for that month that states I paid in full. I submit these statements as claims to my insurance to put toward my out of network deductible.
Sometimes these claims would not process right away but would usually eventually be processed. If it took a while and I would call the insurance company to see what the problem was, I was told the codes were incorrect, even though they were the same as they always were and the same as claims they previously approved no problem. Usually after calling they would re-review the claim and approve it so I thought they just needed a second set of eyes on it or something.
Based on the dates of service, I should have met my out of network deductible back in July. However, by the beginning of September they still had not processed my April or August claims. I called again and after an hour of back and forth, holds and transfers, I was told that apparently what they meant by the codes being incorrect (but they never gave me more information than that before) was that my provider lists ICD-9 codes and ICD-10 on the statement, and they want ICD-10 ONLY. If the ICD-9 ones are removed it should process no problem.
So I had my provider give me new statements for April and August with only the ICD-10 codes and my insurance approved the claims. In my insurance portal if I look at those claims it now says that insurance “paid” a certain dollar amount (remaining deductible and then 70%) and I am responsible for the rest. Since I paid my provider in full at the time of service I was expecting to get reimbursed. I called the insurance company and they said that since they processed everything September 18th, they consider that to be the day my deductible is met and any dates of service before that will not be reimbursed.
I explained that in those claims on their own website it states that they pay a portion and I am responsible for only a portion but they still said they will not reimburse any dates of service before September 18th which is when they processed my deductible being met. But if they had processed the claims when I submitted them it would have been sooner, and if based on dates of service should be July. I asked about what will happen when I submit my claim for September which will have a date of service before the 18th and after and was told they will not reimburse for the one before.
Am I crazy to think that my deductible being met should be based on the dates of service, not when they got everything processed on their end? Am I just out of luck for not being more on top of it and getting this sorted out sooner? Should I approach any of the submitting claims to get reimbursed process differently in the future to make things smoother? Any advice or comments would be appreciated, even if it’s just that I don’t understand anything about insurance and there’s nothing I can do.