I think the answer to your question about Sir John Croker of Lineham (d. 1508) and his two wives can be found in the material of the Yeo Family Society which you mention. See here:
http://www.yeosociety.com/yeoroots/early%20origins.htm#robalice
This should bring you to the section titled “Robert Yeo (145) and Alice Walrond”. The discussion of the 1507 marriage contract between Sir John Croker and Elizabeth Yeo is at the bottom of this section. Here is the text:
“Robert Yeo, his extended family and friends also contracted his daughter, Elizabeth Yeo, then only in her early twenties, to marry Sir John Crocker, of Lynham, Kt., an elderly but prominent man in his seventies. In return Robert and his associates were given lands in Plymouth for the term of her life. The marriage contract dated 4 th July, 1507 was between, 1 John Crokker, knight , 2 John Bassett, knight, Thomas Haycche, Roger Graynefeld, William Walrond, Edmund Yeo and Edward Yeo for the Manors of Hemmerdon and Bykeford for life of Isabel, daughter of Robert Yeo , esq and the witnesses were Humfrey Fulford , Thomas Graynefeld , knights, and William Yeo , & others, all well known names.
“Sir John Crocker's son John had married Ann Arundell , a very wealthy heiress, whose inherited lands included Huish and manors in Stratton, Cornwall and no doubt the Yeo family were keen to share this inheritence. However Ann died, childless, on the 25 th August, 1507, just a few weeks after the marriage and all the estates were shared between other distant relatives so poor Elizabeth was sacrificed in vain.”
The important point is that, at the time of the 1507 contract, Sir John Croker’s son John was an adult, already married and left a widower. Thus. John must have been a son by Sir John’s first wife Elizabeth Fortescue, who is identified in at least some Croker pedigrees. The pedigrees seem to agree that the younger John Croker married (as his second wife) Elizabeth Pollard, from whom subsequent generations of the Crokers are descended.
None of the Croker pedigrees that I’ve seen is entirely accurate, and some of them are wildly speculative. For example, the Croker pedigree on p. 550 of Thomas Westcote, A View of Devonshire (mentioned elsewhere in this thread) seems to split Sir John Croker with his two wives into two separate persons with different wives. And it places the second marriage a couple of generations after the first, and gives him 5 children by Elizabeth Yeo – highly unlikely since the marriage was in 1507 and Sir John died in the following year 1508.
The only Croker pedigree I’ve seen that mentions both wives of Sir John Croker (in the same generation) is that of J. L. Vivian in his editions of the visitations of both Devon and Cornwall. But Vivian mistakenly assigns the second wife Elizabeth Yeo as the mother of the younger John Croker – not possible as discussed above. So, Vivian is likely the source of the confusion about the mother of the younger John Croker.