Fixed issues where a List with the same data but different instance would cause "Model Unstable"

[jrote1]

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CLAs look good, thanks!

[googlebot]

We found a Contributor License Agreement for you (the sender of this pull request) and all commit authors, but as best as we can tell these commits were authored by someone else. If that's the case, please add them to this pull request and have them confirm that they're okay with these commits being contributed to Google. If we're mistaken and you did author these commits, just reply here to confirm.

[jrote1]

I authored these commits

[googlebot]

CLAs look good, thanks!