Permalinks error – post name with ampersand

My site does not appear to be generating permalinks properly.
It indexes legal cases, using the case name as a post title. This works happily 98% of the time

The problem arises with case names which include Ampersands and semi colons
eg
HIGGINS V J & C M SMITH (WHITEINCH) LTD; HL 1990

This generates a pretty permalink (incorrect)
higgins-v-j-hl-1990

What has happened is that the correct attempt to remove the & removes it and whatever follows up to the next semi colon.

It appears that this anticipates that the ampersand will have been escaped and rendered with &

Instead of removing ‘&’ it removes ‘&*;’

I assume that this was an attempt to cope with several possible escaped characters (' etc), but the generalisation is incorrect.

This is a huge problem to me. My site works only because I can predict permalink in advance before updating a case – any case may refer to another (someties) thirsty cases by this permalink.

Is this an error – have I got it wrong?
If not what do I need to do to see that it will be fixed? I anticipate that once the error is located it would take five minutes to correct, but recognise that there is a certain amount of admin to do first.
How will I know whether it will be changed. If it is I can live with it for a few week, but if it is not to be changed I must make a long term amendment to my site.

I have tried this on two live sites, and on a local installation on the latest version of WordPress. The error is consistent