This is the answer from support:
[quote]Hi Anton,
We looked at your logs, and it looks like you were correct in suspecting that there is a string character limit of about 200. Anything more than 202 will throw errors. You may want to update to 7.8.2 and see if that improves that behavior, but it looks like you’ll just have to limit your strings or break them up across multiple tags.[/quote]
And no, in 7.8.2 it’s the same…