It looks like you have used this tutorial: Simple nRF24L01+ 2.4GHz transceiver demo
He has recommended an ancient version of the NRF24L01 library but, for that simple sketch, you should use the latest version (as suggested by @TMRh20 as I was composing this.)
You could also set the power on the devices to low with radio.setPALevel(RF24_PA_MIN) to make it less sensitive to power supply issues.
This also looks odd but it may simply be from one of the other sketches you've been asked to try:
Usually it is 16.
EDIT
I've looked again and I can't see anything which explicitly sets the CRC length to 8 in the sketch in post #2. This then indicates either (a) a power supply issue, bad common ground etc. or (b) that the module, possibly because of the cable length, is unable to support the 10MHz bus speed.
The connection diagram in the "Robin2" tutorial (where you appear to have got your initial code) is misleading in that it shows the use of an external supply but fails to show that all the grounds should be connected together. Some NRF24L01 modules have resistors in the SPI lines which limit the maximum bus speed, as can long cables, and can cause erratic performance. The trouble shooting guide linked in post #30 shows how to configure a lower SPI bus speed.