[Solved] incompetence of CMS help!!!

i have 1 daughter age 19 with ex-wife and another son age 8 with my current partner (I am separated from). My case with Child maintenance service and previously CSA has been going on since 2008. I have always paid ex directly into her bank account every month since 2008. Since 2017 I have had issues with the Child Maintenance incompetence of calculating correct payments. In 2016 I received my payment schedule for 2016/2017 which was fine and set up the new amount from my account. As you can see on the attached letter there are no arrears on the account. In 2017 I received a letter from them stating I had arrears of £3200 (also attached) I called them and was advised this was due to them changing over from CSA to child maintenance services and the arrears were from no payments being made between 2008-2014. I argued this as:
1. If I had not paid in the 6 years ex would have been on my case asap, she texts me if the payment is 5 minutes late!!
2. They would surely have taken me to court or done a deduction of earnings?
I was asked to send in my bank statements showing all payments and then this would go in for review. I had to request all my old statements (some from closed accounts) and had to pay for these and sent them in to the Child Maintenance, even some of the payments were made to CSA direct by Direct debit but they seem to have no record of these. I was told that in the meantime I would still need to pay my normal amount of maintenance and the arrears, which I did reluctantly. I sent these in April 2017 and asked them to look into my case and send me a breakdown of the arrears and where they have got the figures from. I received nothing. After numerous calls and letters to them I still received no breakdown of where the arrears had come from and how they calculated it to this amount. In June I called them and they confirmed that the case had been looked at and that I had overpaid by £370, I asked how I get this back but as I pay ex direct I have to take her to the small claims court, which I don’t have the time or money to do, so guess I have to just lose the money. I was told I would get a letter stating the case has been closed but yet again still waiting for this letter.
In October 2018 I received another letter stating ex had opened another case as daughter had started college (for the 3rd time on another course, she has been in and out of college for 2 years bu ex still claimed child benefit) it stated I had to call and give my details which I did and that the case would go to a team to work out payments. I paid a one off payment in October but it was November before I received a payment plan (which was wrong) I asked for them to re-assess the payment plan as they had not taken into account my other son I pay for and also they were charging me £40 extra for collect and pay when both myself and Marion have stated that we are doing direct pay and not going through them. Yet again they have said there are arrears on the account of over £1000 from October 2018 even though I agreed to pay ex £150 pm whilst they sort this out. I am still waiting for this to be corrected. 2 weeks ago my daughter finished college and started full time employment, Child maintenance were informed and because ex has not informed Child Benefit I still have to pay. I have refused to pay £150 payment and have expressed this to them as yet again don’t want to overpay and not be able to reclaim it back. They have now said the other day I need to provide all my bank statements from 2016-2018 which I have done to prove I made payments and to make sure I paid the right amount.

This seems to be dragging on and on and over the last year has made me ill and caused the breakdown of my recent marriage. I am at my wits end with Child Maintenance as no-one seems to take responsibility for my case or working out correct payments. I fell I am going to be hit with a mass amount of arrears even though they have the evidence of payments.
Parents without care seem to be penalised when they pay regularly, and the government really need to shake up this whole system.
• My daughter has been in and out of college for the last 2 years, but I have questioned this with Child Maintenance but they won’t investigate as ex has not stopped Child benefit (which she should have done as she was committing benefit fraud)
• I have overpaid, but cannot claim this back as need to take her to small claims court which will cost me time and money
• My case workers seem to change every week, and no-one seems to take responsibility for my case
• The case has finished but still want payment and I am now worried they will deduct out of my wages
• Complaints I have made have not been followed up and responded to.

I would like some help or advice on where to go from here as the Child maintenance service have been abysmal and now do not have a good relationship with my daughter or ex due to their incompetence.