Can chromosomal crossover undo itself?
Good thinking. Yes, it is theoretically possible. It is often modelled like this. Have a look at this answer for the maths.

Note however, that to my understanding (and I might be wrong) there is typically either 0 or 1 crossover per pair of chromosomes as cross-over is directly related to the way homologous chromosomes bind together during prophase I of the meiosis by the synapsis. My confusion lies in the fact that, I think, there are sometimes (often?) several synapsis per chromosome pair. Hopefully, someone else will be able to clarify this for us.

As a consequence, the genome-wide recombination rate in humans is almost exactly 23 in humans (Wang et al., 2012). So in practice, such mulitple crossover would very rarely (if ever) happen.