I would recommend you stop trying to make this work if you are using version 6.68 or earlier. PVsyst simply won't allow you to misalign trackers to the south, east to west, if you're using backtracking.
But this is a problem of the software as real fields can't be restrained to accept "only" what the software accepts. There are numerous projects where we have installations with such layout thus impossible to obtain a relevant information related with the expected energy yield to perform analysis of data etc. One thing is what the software permits to allocate and the other thing is reality. And since reality is what should drive development that is the reason we keep asking for a solution or if there is any alternative idea.
In PVSYst 5.74 for example it is stated clearly that for the tilted axis tracker:
Tilted axis: the Phi angle around the axis is adjusted for no shadings conditions. This doesn't allow for misaligned arrays.
(Under Help/Near Shading/Backtracking strategy)
Same is also said in the PVSyst 6.68 help BUT when you make a misaligned tracking plane system has no problem calculating the shadowing using backtracking option (providing a table of linear shadowing with a factor of 1 at all inclinations). So there has been development on this approach hence it is only applicable one way. Therefore any reply from someone from PVSyst development team would be highly appreciated.