The Penn Treebank Parts of Speech tag set differentiated between the base form of verbs (VB), and the non-3rd person singular present form (VBP).
Consider the following cases, with the different uses of rise:
base form: The share price will rise.
non-3rd person singular present: The share prices rise.
In both cases the forms are the same.
All the examples I have seen of verbs where that is not true, are with verbs that can be considered (by some definition) to be modal and/or auxiliary. Such as: be, am, are, is, was, were, being, can, could, do, did, does, doing, have, had, has, having, may, might, must, shall, should, will, or would
Are there examples of words from outside my modal/auxiliary list, of non-3rd person singular present forms that are different from their base forms?
I would particularly appreciate referenced answers, sourcing any statements about their nonexistence/rarity.