hi,
I also had problems with the data integrity over short distances, I tried a number of changes in order to improve the data TX,RX.
Any other electronic equipment working nearby to the RX can cause data corruption.
If your data integrity is so bad, it is possible that the attempted ACK TX/RX back and forth, will never succeed.
Finally I gave up and converted my project to the HC12 TXR module, this works well thru walls, the TX is located in the garden shed about 20 mtrs away.
The HC12 is claimed to work upto a 1000 mtr range.
In case you do not have a copy, I have attached a NRF tutorial PDF, which may help.
Eric