Pictures with cell links slowing workbook

[Bob]

I use the camera (copy >shift edit > paste picture link)
in a number of workbooks. Each picture will link to a tab
within the same workbook.

Suddenly, all the files that contain these links slows
down. It takes longer than usual to open a file, swiching
between worksheets and adding or deleting rows (the row
changes are not in the link).

I checked the system resources and on average have 60 to
70% free.

Any theories on what could cause this?