IMHO the probability of that is zero. If you buy something from a manufacturer and it doesn't work, the standard practice is to get a free replacement and I see no reason whatsoever why that would not apply in this case.
This is especially true when the product has an unavoidable need to be "tweaked" in a small percentage of cases.
SIAL is a highly respected company with some of the best quality control in the world but the problem is inherent in the nature of the way zinc fingers work. It is really a very minor problem when considering how vastly superior zinc fingers are to other methods of genetic modification:
Which approach would you try:
One that worked in a completely exact manner in a very short time **with multiple genetic modifications at once**(3 months or so counting time from first order) the great majority of the time, and when it didn't, could be "tweaked" and would work the second try in a few weeks (at no additional cost) --- multiple GMs in just a few months with exact locations(zinc fingers)
Or one that was completely random, took months for each attempt and multiple tries for each genetic modification and might not work at all ever and each genetic modification had to be completed before starting the next one. --- Years (if ever) for multiple GMs at random locations where the GMs might not even be functional
Obviously you're going to use zinc fingers and, in perspective, the outside chance of having to spend a few extra weeks for a "tweak" is totally inconsequential considering the alternative!
As I said: a need for tweaking probably won't happen, but if it does it will be only a minor and temporary setback (and quite possibly a buying opportunity as well if enough ill-informed weak hands panic) Sometimes you can see such a possibility for a buying opportunity in advance and I try to arrange to have some cash on hand in case it occurs. If it happens I will be here pointing out that it's only a temporary problem but if a selloff happens, I'm buying.
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