Clarice DE LA WARRE (de Tregoz) - Incorrect parentage?

The problems, as far as I can tell, are coming from dates that cannot be sourced, that is, for which there would be no evidence. Because there would have been no records. So the problem isn’t the connections, but the dates themselves. Which got invented at some point. Death dates can be real dates at this time, marriage dates very seldom unless it’s an important state marriage, and birth dates almost never.

Here’s a citation for you, Craig Andrew Miles

G.E.C. Vol IV. Complete Peerage. 1916. Pages, 139-41. La Warr, now De La Warr. < Archive.Org > Sir Roger la Warre,(e) of Wickwar, co. Gloucester, Brislington, Somerset, Milton, Folkington, Isfield, &?c., Sussex, s. and h. of Sir John la Warre (living 27 May I277),(f) of Wickwar and Brislington, by Olimpia, da. of Sir Hugh de Fokinton. … He m., in or before Sep. 1276, Clarice, elder da. and coh. of Sir John Tregoz, of Ewyas Harold, co. Hereford, AUington, Wilts, Albrighton, Salop, Great Doddington, Northants, &'c. [Lord Tregoz], by his 1st wife, Mabel, da. of Sir Fulk FiTz Warin, of Whittington, Salop. She was living in Apr. 1289, (d) and d. v.p., that is, before 28 Aug. 1300. He d. 20 June 1320. (e)

I eliminated 1250 birth as perhaps too early, but it’s more likely the dating issue is at the parent generation. You could look at https://cybergata.com/roots/7611.htm for more references on the Tregoz line, but you have a marriage date of September 1276 as a constraint.