Indusoft IWS8.1 tag invalid expression

Hi,
Sometimes tags become bad quality and their value is Invalid Expression, these could be tags that have been working for weeks no issue and its only basic writing a value to them and displaying it. Restarting the service won't fix this issue, neither will trying to change the value in database spy.

I removed all usage of the bad tags and then try to change the value and it still doesn't change, how can I revert bad tags? Any way to see how they became bad in the first place because I can't see what has caused it. I noticed it happens most after the service was stopped and started again after making changes on something unrelated.

Any help appreciated this is driving me mad.

Note: Creating a new tag and updating all positions will fix the issue but another tag with become "bad" some unknown time later.
Is it possible to manually delete individual tags as well rather than remove all unused? I'm wary that I could remove unused tags which the system thinks aren't used but they are, how reliable is the "remove unused tags" function

anyone?

Can't say I've encountered this... (but then with Indusoft there is always another surprise waiting) What service pack are you using?

I recommend you contact Indusoft support.

its not that reliable.. you might be using indirect addresing and indusoft will consider as unused tag..

I personally never use that feature..

You should contact indusoft online chat support, they are usually online and very helpfull,

Have you done a Verify with remove blank lines checked? That sometimes messes with things.

What communications protocol are you using? We do a lot with CoDeSys and symbol files and those sometimes get messed up.

v8.1 sp4, I just tried the chat that I didn't know existed,
Support advised me to check the output window for field read/write next time the issue happens. He thinks it may be communications related (SIETH would be the offender if that's the case), though sometimes the tags aren't even used on a driver sheet so I'm not sure. One thing I noticed just now is that I created a tag the other day onto a SIETH driver sheet, the tag is one of the "bad" ones now, the tag is nowhere to be seen on the tag list, if I type the tag in some script and check it says the tag doesn't exist, but if I type the tag in the driver sheet it doesn't prompt to create a tag on the fly, which means one half of indusoft recognises that tag exists and the other half doesn't.

Not used Coedsys or verify if that helps