The burden of proof is on their ends not your. As
long as you meet their image format specification, you
are safe. I imagine you taken the digitcam pictures
and upload  to their Website through the offended
button. Your task is ended at that point. The rest
depends on how clever the Millers Lab's java  Developer
team.

For on the safe side, if your colleagues claim there
is no problem. You then need to upgrade your software
to meet Millers Lab spec. If the Millers Lab claims
nobody else have the problem except you, then I think
something deeper than technologies.

For your question, the computer language errors are in
the two main categories: compiling and running. In
Java's compiling represent javac and running represent
javax. In javac phase, computer automatically catch
the errors. In javax  phase, computer sometimes can
missed the error. Since your situation is an
individuals against an organization, the burden of
proof is on the organization because it has the
resources to cover the problems  generated by the
individuals.