it is quite upsetting because now we don't know how much they are taking from us for their own pocket.
Nobody is taking anything from you. Take note that the "earnings figure" reported in the AdSense dashboard is "Estimated Earnings", which means it is subject to change at any time for any reason. Invalid clicks are "invalid" they do not count never have and never will and there is no way to suggest that they should.
If a bot is clicking on your ads, that's not valid.
If a user starts clicking on the same ad 20000 times that's not valid
if you by mistake click on your own ad that's not valid
if for what ever reason the clicks are invalid, then that is it, it is not your money never was and never will be. Accept, make peace with. There is nothing wrong with this, at has always been the case. Could AdSense be more transparent as to the source of the invalid clicks and provide more support in stopping invalid clicks? Yes definitely. But that is not the same as suggesting that somehow you are entitled to money that you didn't earn.
But more important than the fact that the money was never yours is that in the event of frequent and high value of invalid clicks, it is solely your responsibility to stop these clicks from taking place, that is blocking bots, fixing your layout, blocking malicious users, not clicking on your own ads, what ever. You need to deal with the problem.
since I joined them years ago i secured the most %.
The payout hasn't changed, it remains 68% for everyone.
Also, they are really behind in sending the monthly check. Still nothing!
Are we talking about AdSense? In all the years I have been with them they have never been late. Not once. Is it possible there is an issue with your payment method? Have you been receiving payments by Western Union? AdSense no longer pays via Western Union since about a year. Have you reached your earnings threshold?
AdSense has many faults, but none of the issue you raised is a fault. In terms of trustworthiness, pay out ratio, and timeliness of payment, there is no better than Adsense, possibly equal but not better, and there are certainly far worse networks out there, far far worse.