As @jlawler pointed out when this question was originally asked in the Linguistics Stackexchange, the Oxford English Dictionary has dated examples of the use of both repair-1 "to return" and repair-2 "to fix" (the latter is the meaning that survives now, but it is numbered 2 in the OED because it is first attested 50 years later in the 14th century).
The terms coincided in Middle English (1325 for #1, 1387 for #2), and can be treated (just) as the same meaning: the transitive means "to put something back to the situation it was before", the intransitive "to put oneself back to the place one was before". OED however points out they were distinct in Anglo-Norman, and etymologically: repair-1 was repeirer, reparier, repairir, repairier, repairer, from Latin repatriare, while repair-2 is Anglo-Norman reparer, from Latin reparare.
Contra @jlawler, the dated examples in the OED do not establish when repair-1 fell out of contemporary usage, since in fact it survives in jocular usage, as a deliberate antiquarianism:
2004 Ireland's Own 19 Mar. 15/2 In bygone times, the men repaired to the local tavern after church to drink the ‘pota Padraig’.
Hence https://en.oxforddictionaries.com/definition/repair listing this sense as "humorous, formal".
It's very hard to intuit when usage passes from current to self-conscious and jocular, but looking at the citations in OED, I would guess early 20th century, which is consistent with the timeframe of H.G. Wells. The following for example looks serious and not jocular:
1911 J. G. Frazer Golden Bough: Magic Art (ed. 3) I. v. 250 When the rains do not come..the people of Central Angoniland repair to what is called the rain-temple.
Answering why a word sense became obsolete is always tricky and guesswork. The fact that there's a slightly confusing semantic difference between "restore something to previous situation" and "restore oneself to previous location" does not help, although the Middle English merger of the two verbs was tolerated for 6 centuries, so it does not explain why the plug was pulled on repair-1 when it was. The synonymous "retire" also sounds stuffy to contemporary ears, and repair-1 likely became restricted in the 19th century to a particular social context (aristos repair to the drawing room, plebs go or return), which would have also encouraged obsolescence.
