What you call a lot of excursion is simply due to the fact that, now, for an unknown reason, your string is really moving freely. The chorus effect is certainly a twisted when fitted string, quite easy to correct, simply release the tension and put the string backwards a bit, you will notice that it's twisted.
It's not against you, but a lot of people including some repair shops are mounting the strings by turning them around the post, so twisting them and thus creating that chorus effect (which as you wrote could also come from a too close pickup). If you mount your strings this way, it's ok as long as you untwist them the way I explained above.