evaluation – Formula: setting parameters vs replacement, different results?

I have a question that may sound stupid and have an easy answer – but I currently do not see it.
I have defined a function of four variables, $f[a,b,c,d]=…$, in what I think is correct Mathematica syntax. I need to evaluate this function at specific values $a*,b*,c*,d*$ for $a, b, c, d$. When I do so, I obtain $Indeterminate$ as a result. However, when I evaluate $f$ at the specific values for $a, c, d$, and only replace $b$ for its value afterwards, $f[a*,b,c*,d*]’ /. {b rightarrow b*}$, I do obtain a reasonable result. Any explanation for this?

PS: I can share the snippet, that shouldn’t be a problem. However, perhaps there is a general explanation and hence no need for it…? I have seen Setting the parameters in a defined function vs replacement rule in the formula, which basically asks the same question, but I don’t think the answer is satisfactory. In any case, thanks in advance.