Let me elaborate on @DanMills suggestion:
(a little too long to fit as a comment)
Altium SCH historically used a unit-less grid spacing for schematic (DXP Units).
All SCH symbols were made using the default pin spacing of something like 10-units. All was well.
Then a awful decision was made to add units to SCH drawings. Nobody can really justify why this would be a "Good Idea"(tm).
DXP-units became 'mils' and an option of 'mm' was added as an alternate grid.
Now whenever a new unsuspecting user chooses 'mm' as their SCH or library grid, everything breaks when trying to connect wires. The root cause involves rounding errors when switching from metric to Imperial grid settings.
Use only the Imperial grid in SCH and SCH libraries! Otherwise you are on your own, and all previously made SCH libraries, and most previously made SCH parts, will be off-grid.