Having a bizarre INDEX/MATCH error I cannot resolve.

In range A1:A20 I have the list of percentages shown below (with corresponding numeric values for each in B1:B20. These column B values are irrelevant, but you could simply use 100.000 for each in column B as it really doesn't matter since the error is during the MATCH check.

3.000%
3.125%
3.250%
3.375%
3.490%
3.500%
3.625%
3.750%
3.875%
3.990%
4.000%
4.125%
4.250%
4.375%
4.490%
4.500%
4.625%
4.750%
4.875%
4.990%

In C1:C20 I have the corresponding "numeric" (non-percentage) value of the percentages in A1:A20, i.e. 3.000, 3.125, 3.250, etc. In column D I am doing a simple INDEX/MATCH function to find the lookup value of C/100 in the A column, and then returning B value.

I work with INDEX/MATCH all the time in a variety of projects, and the only time I legitimately get an error is if the lookup value is in fact NOT in the lookup range, or there's some data formatting issue and I need to apply some TRIM/CLEAN functions to resolve.

For the above range of %'s, all return correctly except 3.99%. I can confirm and validate a boolean TRUE/FALSE statement that (C10/100) = A10, but my formula is still returning a "no available value" error for:

=INDEX($B$1:$B$20,MATCH((C10/100),$A$1:$A$20,0))

No idea why and no guess as to how and resolve since it is not a data formatting problem that could be cured with TRIM/CLEAN. Any suggestions???