Could be GR didn't want further equity exposure to crb at...

Could be GR didn't want further equity exposure to crb at the time of cr as they simply saw it as being outside their core business, which is after all engineering. Better use of their capital inside their business or elsewhere.
If their sell down has been through everyday trading and not a trade, block style sell to another cornerstone investor, as you suggest, then that does seem noteworthy.
There may well be frictions at this shareholder level.
Managed to reach a new sp low yesterday at 2.3. This in the context of a raging bull market in critical minerals. Not good.