To follow on this saga ...
Went to collect the oil from the greasy spoon, having been told it was all dry and liquid ... yeah, right.
About 10, 20 ltr drums, all with the tops missing some overflowing with thick, yellow, frozen fat.
I had higher hopes for the lidded 100 ltr barrel, but no, exactly the same in there. Now got a dilemma as to process in this weather or not.
Anyhow, spent quite a while today carefully doing Dr Pepper tests. First one was with 500ml of really good oil and a base of 3.5 ASM from drum 1 ...

"Special reserve oil"

Half the ASM/Methanol added and shaken lightly ... interesting to see the separation despite the shake.

After vigorous shaking.

Completed reaction
So, the DR Pepper worked OK. I didn't do a 3/27 test as I only wanted to check I wasn't making soap!
Next test was poor quality oil, very similar or the same as the first batch which went wrong ... that too gave a non soapy, good result.
So thinking now is it's got to be my process.
I'm interested in the light brown, almost opaque emulsion looking mixture after the vigorous shake. I have noticed this, along with a soapy texture, on full size batches if you take samples during or immediately after adding the metoxide. As with the Dr Pepper above, this clears if you carry on adding catalyst and continue to process.
Anyone else noticed this before?
With the above in mind I decided to do a Dr Pepper on the last batch to go wrong. This was still liquid in cubies outside. As I'd added about half the catalyst, I did a Dr Pepper using the 50% base ASM and 50% Methanol (although it was Methanol rich from my attempts to recover it). This test too produced a full reaction with no noticeable soap.
So I'll be having a go at reprocessing the last batch to see if I can get it to complete.
I'll stick further thoughts in a new post, this one's getting rather long!