Pantone colours look visually different between versions of colour books

Hello,

When opening the same pantone solid coated colours from 2 different versions of the books they look visually quite different. For example a customer has sent me artwork that has 7546C in it from the "previous version" book. If I choose that same colour from the Pantone+ Solid Coated-V4 book it looks a lot darker. The darker version visually looks coser to the actual PMS book i have here and that would also match the mixing system version of the actual ink. But if a customer is choosing a colour based on what they see on the screen and dont have a physical colour book this could cause some issues.

Seems very odd that the colour wouldn't look the same across different versionsof the books.