csv.Sniffer().sniff() guesses "M" for the delimiter of the first dataset below. The same error occurs when the "," is replaced by "\t". However, it correctly guesses "," for the second dataset.

---Dataset 1----
Invoice File,Credit Memo,Amount Claimed,Description,Invoice,Message,
Sscanner ac15072911220.pdf,CM_15203,28714.32,MX Jan Feb,948198,,
Sscanner ac15072911221.pdf,CM 16148,15600,MX Unkwon,948199,,
Sscanner ac15072911230.pdf,CM 16148,33488,MX Cavalier,948200,Photos don't match the invoice
Sscanner ac15072911261.pdf,CM_14464,1713.6,MX Dutiful,948203,,
Sscanner ac15072911262.pdf,CM 16148,3114,MX Apr,948202,,
Sscanner ac15072911250.pdf,CM_14464,1232.28,MX Jan Feb,948208,,
Sscanner ac15072911251.pdf,CM_17491,15232,MX Unkwon,948207,,
Sscanner ac15072911253.pdf,CM_14464,11250,MX Cavalier,,,
Sscanner ac15072911253.pdf,CM_14464,11250,MX Dutiful,,,
Sscanner ac15072911253.pdf,CM_14464,11250,MX Apr,,,

--- Dataset 2---
Invoice File,Credit Memo,Amount Claimed,Description,Invoice,Message,
Sscanner ac15072911220.pdf,CM_15203,82.07,MX Jan Feb,948198,,
Sscanner ac15072911221.pdf,CM 16148,23.29,MX Unkwon,948199,,
Sscanner ac15072911230.pdf,CM 16148,88.55,MX Cavalier,948200,Photos don't match the invoice,
Sscanner ac15072911261.pdf,CM_14464,58.78,MX Dutiful,948203,,
Sscanner ac15072911262.pdf,CM 16148,52,MX Apr,948202,,
Sscanner ac15072911250.pdf,CM_14464,40.40,MX Jan Feb,948208,,
Sscanner ac15072911251.pdf,CM_17491,54.97,MX Unkwon,948207,,
Sscanner ac15072911253.pdf,CM_14464,4.08,MX Cavalier,,,
Sscanner ac15072911253.pdf,CM_14464,49.11,MX Dutiful,,,
Sscanner ac15072911253.pdf,CM_14464,18.28,MX Apr,,,