This is another issue that raised many objections among the critics of the Bible. Another chance to disprove and discredit the Bible. I googled a little about this problem but I didn’t find anything positive, other than some try to equate Mount Hor with Moserah. Yet, that seems quite improbable since “there is a significant amount of travel between these two points”, as Wikipedia rightly observes. So here is a quite satisfying interpretation:
For example, one of the many objections raised against the historical reliability and integrity of the Pentateuch dealt with an alleged conflict of tradition in regard to the place where Aaron died. According to one of the sources that scholars purported to identify, he died on Mount Hor (Num. 20:22; 21:4; 33:33; Deut. 32:50), but according to a “different” tradition he died at Moserah (Deut. 10:6). A careful reading of the text shows that in point of fact there is absolutely no conflict in the tradition concerning the death of Aaron at all. The word מוֹסֵרָה in Deuteronomy 10:6 means “chastisement”, thus describing the place of his death in terms of a value judgment. This allusion makes it clear that his decease on Mount Hor constituted a reproof for the trespass at Meribah (Num. 20:24; Deut. 32:51), and that, like Moses, he was excluded from the Promised Land because of his rebellion against God. The two supposedly conflicting traditions are thus in complete harmony, and preserve the facts that Aaron died on Mount Hor while the people encamped below in mourning. In order to mark this sad occasion, which, with his own exclusion from the Promised Land, lay heavily upon the mind of Moses (Deut. 1:37; 3:23ff.), the incident and the camp-site were designated Moseroth (Num. 33:31; Deut. 10:6).
In this connection it should be noted that the various references to the death of Aaron (Num. 20:22ff.; 33:38f.; Deut. 10:6; 32:50f.) are supplementary rather than contradictory. While they are rather different in nature, they are by no means inconsistent in their presentation of fact. Although in the strictest sense Mount Hor was the physical scene of the death of Aaron, the name “Moserah” or “Moseroth” described the character of that event as “chastisement” (G. T. Manley, EQ, XXVII (1955), pp. 201ff). That this word was used as a common noun is indicated by the plural form in Numbers 33:30f. Like Massah, Meribah, and Taberah it denoted the nature of the event as well as the place where the incident occurred.