My sense is that red shift is on pretty solid ground, but the questions do exist and some are interesting. If there is an error in our understanding of red shift it would deeply change our corresponding sense of the universe.
If the universe is expanding, redshifts should show a continuous range of values. Instead, however, they are “quantized,” i.e., they tend to be multiples of certain basic units, the main ones (expressed as velocities) being 72.4 km/s and 37.5 km/s. This phenomenon, says Arp, “is so unexpected that conventional astronomy has never been able to accept it, in spite of the overwhelming observational evidence” (p. 195). He suggests that redshift quantization could be due to episodes of matter creation taking place at regular intervals.