Continuity mistake: While on the boat, Helena does her 7 spades card trick. When she gives Indy a turn, you can see the bottom card is a black 2. When she fans them out, it changes to black king of clubs. Then, in the next shot, it changes to 8 of clubs. (01:16:00 - 01:17:00)
Suggested correction: Not necessarily a mistake. She could be changing those cards by sleight of hand, while moving the 7 of spades into position for the final force. The mistake was not using the 3 of clubs for it.
Other mistake: In flashbacks, younger Indiana Jones has exactly the same voice as the older one.
Suggested correction: Harrison Ford's voice has always sounded the same. Watch any film he's done.
It's a noticeably "older" voice than in previous films when he was about the age his de-aged self is meant to be. I mean he's now in his 80s not 40s, of course his voice is different! An unavoidable mistake but still clearly different.
Actually, it is easily possible to augment his older voice to sound young. If his older voice is too deep, for example, Ford could merely speak slightly slower when recording the dialogue - and then it could be sped up slightly in the final cut. Or, audio AI can be used to alter voice patterns as desired nowadays (ex. To remove the 'gravelly' aspect of his voice).
Harrison Ford's voice has definitely become pretty gravelly.
