I have 2 companies which had splits and i recorded split just fine, but after selling the positions something wierd happened.

Both of those companies with split has now quantity of 0 after selling the position but Value is small positive amount.
For example I had Brookefield infrastructure (BIPC).
27.8.2021 bought 67 of them
13.6.2022 split 1 to 1,5 (to 100).
20.12.2022 sold 100.

Now I have in portfolio 0 BIPC with value of 27,61 $, and I do not know how to fix that.

same applies to
Waypoint reit.
4.6.2021 bought 780 WPR
10.11.2021 reverse split 1 to 0,9372
21.11.2022 sold 731 shares

Now I have 0 WPR with value of 0,05 $

First, what version of KMM are you using, and on what distro or OS?

Next, a 1 to 1.5 split of 67 shares gives 100.50 shares, not 100. What price precision is set for it? There might be rounding issue. Probably not relevant, but what was the price of SIBC on the purchase date, the split date, and the sale date? You mention the value of the stocks after the sale, but not the number of shares (not really zero) or price.

Similar for Wyapoint, 780 shares with 1 to .9372 split gives 737.0160 shares.

My advice is first to increase the price precision so you can actually see the residual shares. Then, you can either sell the actual number of shares held, or else do a "remove shares" just prior to the sale. That is not really accurate record keeping, but all the dollar amounts to match the bank statement.

Also - have you looked at your statement or online record to see what the bank/broker says about the actual share counts?

5.1.3 windows.
Yes I figured out its rounding issue, but how to fix it? The fractions are at 1/1 and price precision is 5. In splits usually fractional shares are not issued but paid in cash instead. So when split is recorded the fractional shares should be discarded. how the split works in Kmymoney is wrong. It should not keep fractionals.

I'll probably create a wishlist bug report to allow a split-shares transaction to handle removing partial shares and putting payment for them into the brokerage account. For now, I suggest you add a sell shares transaction right after the split, selling the partial shares for whatever amount you were credited. However (I have not yet tested this) I would be very careful that KMM recognizes the sale as after the split, so it might be necessary to make it the following day to be certain. In general, the actual order of transactions on one date don't really matter, but if one of them is a split, it does matter. You can enter the share price as part of the transaction, but there is no way to specify whether the number of shares is before or after the split.