There have been a few reported issues of “floaters”, the explanation given was that this was the result of the filtration setup pulling fibers off the back of the filters being used. They claim to have made process changes to correct the issue. I don’t recall anyone reporting floaters in the last several months.
There was one reported incident of foreign material in a vial that looked concerning. The explanation for that was something to do with material from the stopper. I’ve seen no other similar reports and the vendor agreed to replace the product for that person.
Beyond that, the primary complaints have been under-filled vials and the quality of the stoppers that perhaps led to the issue above. According to the vendor those have also been addressed.
Throughout this time period I’ve used QSC oils from a couple batches. I’ve observed no floaters or issues whatsoever other than again, the under-filled vials and the poor quality stoppers.
Since I tend to run some combo of test and primo, it’s more convenient for me to mix them into a sterile vial and since I’m doing that, I filter as well.
Aside from the obvious benefit of guaranteed sterility, I’ve heard a plausible explanation for PIP being the result of bits of ester not in solution and that filtration will mitigate that.
And finally, since we’re harping on this topic, I’d rather see an implementation of @Ghoul’s suggestion of terminal sterilization rather than some sort of sterility testing done way up the supply chain.