Can you send the exact load table? And the size of the file to be loaded?
In the previous load with a trailing comma you mentioned 12 files. IQ 16 will load each file in the FROM clause in separate threads. If this is just a single file, then the CPU drop makes sense. However, a properly formatted load table should run fully parallel with just 1 file.
Likely, the cause is that you don't have QUOTES OFF specified. The default is ON, kinda backwards in my opinion. Anyway, QUOTES ON means that we cannot load fully parallel as we have to scan each column single threaded looking for the beginning quote and end quote. This is time consuming and is not currently parallel.
Before sending anything, try dropping in QUOTES OFF near the ESCAPES OFF line and see if that works.