Which Jan Abraham Nel married which Elizabeth van Jaarsveld?

@Jan Abraham Nel
@Jan Abraham Nel, b8c1d2e1
@Elizabeth Stadler, b7c6d4
@Elisabeth van Jaarsveld, b7c4d3

When looking at the references below, some discrepencies show up.

Reference 1 and 2 are not in conflict.

The Elizabeth in 3 and 4 has different parents and is not the same one as in 1 and 2 except if the parents in 3 and 4 are wrong. Even if the 2 Elizabeths are the same, then 1 and 4 are contradictory because 1 implies that Jan Abraham Nel is the widower of Elizabeth and 3 implies that Elizabeth is the widow of Jan Abraham NEL. Also the Elizabeth in 1 died before 1821 and Johan STADLER married the Elizabeth in 3 only in 1831.

The above leaves one with 3 possibilities:
a. The Jan Abraham Nel in 1 and 2 is different from the one in 3 and 4. This is not acceptable because 4 gives the same parents as 1.
b. Johan Stadler did not marry Elizabeth, but her younger sister Susanna Margaretha. This is also not acceptable because Jan Abraham NEL only died in 1840, and Johan STADLER already married in 1831.
c. The entries of Jan Abraham NEL in 3 and 4 are just incorrect. This seems to be the case since in both 2 and 4 he married two different Elizabeths on 6.4.1817.

I will approach GISA with this document and treat the situation in the tree such that the Jan Abraham NEL in 3&4 is a different one from 1&2 and that his parents are unknown.

Any other ideas?

1. SAG vol 6c:
d2 Jacobus (Koos-kommandant) (NEL) * Amandelboom, over de Zakrivieren ≈
10.7.1768 † Blomfontein in Roggeveld 13.9.1840 x 10.3.1793 Anna Jacomina VAN WYK
e1 Jan Abraham * 22.10.1793 ≈ 8.6.1794 † c. 1840 x Swartland 6.4.1817 Elisabeth VAN JAARSVELD * 8.4.1795 d.v. Stephanus Albertus van Jaarsveld en Cornelia Geertruy Jordaan xx Swartland 8.4.1821 Susanna Margaretha VAN JAARSVELD * 4.6.1804 d.v. Stephanus Albertus

2. SAF v17:
d1 Stephanus Albertus (VAN JAARSVELD) * 30.9.1790 = 24.10.1790 † Vogelfontein, Victoria-Wes 7.7.1856 x Victoria-Wes 11.11.1844 Anna Catharina Maria HUMAN
d3 Elizabeth * 8.4.1795 = 26.4.1795 x Swartland 6.4.1817 Jan Abraham NEL = 8.6.1794
d5 Susanna Margaretha * 4.6.1804 = 22.7.1804 x Swartland 8.4.1821 Jan Abraham NEL = 8.6.1794

3. SAG vol 12
c1 Johan George (STADLER) ≈ 2.5.1802 † “Welgevonden”, dist. Fraserburg 13.5.1872 (71.-.26) x Worcester 10.11.1831 Elizabeth VAN JAARSVELD (voorheen x Jan Abraham Nel) (Albertus-dg)

4. SAF v17:
c6 Albertus (VAN JAARSVELD) = 11.10.1761 † Riebeek-Kasteel 14.10.1835 x 3.5.1789 Anna Elizabeth MAREE † Riebeek-Kasteel 27.3.1837
d4 Elizabeth = 8.10.1797 x Swartland 6.4.1817 Jan Abraham NEL (Jacobus-sn) xx Worcester 10.11.1831 Johan George STADLER (Adam Decker-sn)