I'm stumped on this one, please help me oh wise stack exchangers...
I have a function that uses xlrd to read in an .xls file which is a file that my company puts out every few months.  The file is always in the same format, just with updated data.  I haven't had issues reading in the .xls files in the past but the newest release .xls file is not being read in and is producing this error: *** formula/tFunc unknown FuncID:186
Things I've tried:

I compared the new .xls file with the old to see if I could spot any
differences.  None that I could find.
I deleted all of the macros that were contained in the file (older versions also had macros)
Updated xlrd to version 0.9.3 but get the same error
These files are originally .xlsm files.  I open them and save them as
.xls files so that xlrd can read them in.  This worked just fine on previous releases of the file.  After upgrading to xlrd 0.9.3 which supposedly supports .xlsx, I tried saving the .xlsm file as.xlsx and tried to read it in but got an error with a blank error message

Useful Info:

Python 2.7
xlrd 0.9.3
Windows 7 (not sure if this matters but...)

My guess is that there is some sort of formula in the new file that xlrd doesn't know how to read.  Does anybody know what FuncID: 186 is?
Edit: Still no clue on where to go with this.  Anybody out there run into this?  I tried searching up FuncID 186 to see if it's an excel function but to no avail...
I had the same problem and I think we have to look at the cells excel that these are not picking up empty, that's how I solved it.
Python XLRD Error : formula/tFunc unknown FuncID:186