I have gone through a silly number of labs now.
Every now and then a lab I trust fails on a COA for a batch we ran R&D’s on for.
I am now in the market for new labs. Landau is one I am thinking of trying. As is Verity.
Any other reputable for flower and concentrate COA’s in CA?
SC Labs has always been good to me
EVIO labs if you are near Berkeley. Discounts on large orders, fast turnarounds, and in house testing (except for PCR sex testing).
Harren’s
2 river labs
I like Pure Analytics in Santa Rosa.
We primarily use Landau because they are closest to us. Never had any issues on cat iii items, but repeatability on cannabinoids seems to be hit or miss.
Expecting labs to get it right 100% of the time is probably unreasonable. There are humans involved. They make mistakes.
Imo what matters is how the lab addresses (potential) errors when the customer doesn’t agree.
Nobody like hearing their product popped for pesticides, and the majority of the “hey you got this wrong!” most labs are actually gonna see from customers probably fall under the “yeah, I know you don’t want to hear it, but…”, where the lab IS correct.
Which will color the lab director’s response even when you do have a legitimate issue with their results.
How are you determining they’re wrong?
What was their response?
We use encore, they’ve been great to work with so far and we get good volume pricing as well.
Where I have had issues is ordering a full panel r&d and getting results like say 25% cannabinoids, ND on all pesticides and metals. Then ordering an official test where the exact same person from their lab pulls the sample and we end up with an official test that is 19% cannabinoids and half the limit on lead. Their response is that it’s a published official coa, it’s your problem now.
Is that due to sampling errors on your part or theirs? Batch inconsistencies? Cherry picking?
Labs can do “R&D” testing on whatever you hand them. They are responsible for achieving a representative sample when performing state mandated testing.
Did they come to your lab and sample in the same manner? Or was the R&D sample a single bud you pulled?!?
This 
We have the lab come to do a “mock” official test. They sample. In that particular case the exact same person came to our site and pulled a representative sample.
Have had this issue multiple times now. With a few labs.
Infinite is the only lab I know that’s actually owned by chemists- science, customer service, turnaround time all second to none