I just tried out using 5 hyperlinks in the same text block without issue in 18.2.1. Did you happen to try and create a new text block and start fresh just to see if that makes a difference? Maybe you can share that page?
If you need something quick, you can just make the text blue and underlined without adding a hyperlink, and add a transparent button over the top for each link?
The process for adding hyperlinks seems quite fickle and troublesome.
I never use the text hyperlinks. They are finicky (as you say) and sometimes hard to click on, because Lectora (and web browsers) treat the blank spaces between words and lines as null, which is irritating.
Biggest issue with invisible buttons is that when designing for responsive, you might have to move them. In fact you have to make sure they are big enough else browser differences might turnmoil it and your element is not clickable anymore. I do use them too though, but you have to be aware of the issues of it… as mentioned before.