I've just adopted Joan, widow of the Lawrence Pabenham who died ca 1398. However, I'm thinking that she was not the Joan who married John Waleys and died ca 1421.
Lawrence Pabenham (i.p.m. 16 June, 22 Ric. II  had a son named Lawrence with a wife named Joan. This Lawrence (jr.) predeceased his father, and his widow Joan held property which was to revert to the right heirs of her father-in-law Lawrence at the time of her death. Lawrence senior's i.p.m. reads:
"Long before his death he enfeoffed by his charter Lawrence his son and Joan his wife and the heirs of their bodies of the under-mentioned manor of Pabenham. Lawrence the son is dead without heir of his body, so the reversion after Joan’s death belongs to the right heirs of Lawrence the father. "
The i.p.m. for Joan, widow of John Waleys reads:
"Laurence de Pavenham, knight, was formerly seised in his demesne as of fee of the manor of Pavenham and granted it to his son Laurence and Joan Waleys, then Laurence’s wife, and the heirs of their bodies, remainder to Laurence the father. Laurence the son and Joan were seised in fee tail and Laurence died without issue by Joan, who remained seised. On the death of Laurence the father the remainder descended to Katherine wife of Thomas de Aylesbury, knight, and Eleanor wife of John Tyryngham as daughters and heirs of Laurence de Pavenham, knight. Eleanor died and the remainder of her moiety descended to her son and heir John Tyrynghan, a minor in the king’s wardship. Joan Waleys died seised and the manor therefore descended to Katharine and John as the right heirs of Laurence de Pavenham, knight."
So I am thinking it was Joan, the wife of Lawrence junior (who is not yet on our tree) that married John Waleys and died in 1421. I'm also wondering who John Waleys was, as there was one who died in 1418 who was married to Joan Turk, daughter of Sir Robert Turk. Are the two Joans the same? John died with 5 underage children, but they might have been by a previous wife, as it seems he was apparently not married long to Joan.
"His wife Joan Turk, whose father Sir Robert Turk had been a wealthy citizen and grocer of London, had inherited through her mother Beatrice the De Kendale and De Boys properties in Hertfordshire and Hampshire. The Waleys did not survive long to enjoy this fortunate addition to their estates. John Waleys II died in 1418 and his young son John Waleys III died within age leaving the inheritance to be disputed over and divided between his four sisters and their nearest male relations.”
Sir Robert Turk's ipm of 1401 notes that his dau. Joan was then 26 and married to John Waleys. This would not rule out an earlier (probably brief) marriage to the Lawrence Pabenham who died in his father's lifetime, as his widow was already remarried to John Waleys by the time of her father-in-law's 1398 ipm.