Posted by Alexander Schwartz on Nov 30, 2019; 11:02am
URL: https://discuss.asciidoctor.org/Bug-loss-of-borders-in-table-when-span-cells-is-used-tp7382p7383.html

There are at least two open issues regarding this...

• Missing Border in Multirow-Cell
• Cell with row span which includes the last row, shouldn't have bottom border

... and one suggestion that might provide a solution to this, there is already a related PR for the asciidoctor-stylesheet-factory:

• Use cell borders instead of table border

Issue #2563 contains a CSS fix that might work for you or might be a starting point for something that works in your situation.

I've tried it locally and adding some pass-through-CSS fixed the example your provided in my preview:

++++
<style>
table.grid-all {
border-collapse: collapse;
}
</style>
++++