That notebook is a mess. It's impossible to read some of the colored highlighted code (and imagine if the reader was color blind). Then there are redefeinitions of all sorts of things. If you want serious attention put into your question, you'll need to do a much better job of pruning and isolating the problem(s).
I will recommend three things.
(1) Make the functions R1 etc. only defined on explicit `NumberQ arguments. This would be done (after quitting or at least clearing the current definitions) as
R1[V_?NumberQ, Kms1_?NumberQ, Kms8_?NumberQ, Kmp1_?NumberQ,
Kmp7_?NumberQ, Keq_?NumberQ, S1_?NumberQ, S8_?NumberQ, P1_?NumberQ,
P7_?NumberQ] := ...
(2) Set the parameters to high precision. For the shorter list this could be done as
Parm2 = SetPrecision[{VR1 -> 0.12, VR2 -> 0.2, VR3 -> 0.2,
VR4 -> 0.6}, 100];
(3) Run FindRoot at higher precision than default (which is machine precision). Could be done as in the example below.
ss1 = FindRoot[
Table[Odes[[i, 2]] == 0, {i, 1, Length[Odes]}] /. RateEqs /.
CoAMATX /. Parm /. Parm2, t1, WorkingPrecision -> 50]
If you have further trouble I will advise that you pay serious attention to the first remarks when formulating any follow-up question(s). This notebook is way too long to go through, just to guess at what might be the problematic areas.
