The man page stylesheet does certain subtitutions, so that for example backslashes in character data appear correctly. But, this doesn't happen when text is inside a link element. For example,
<para>\copy</para>
<para><link>\copy</link></para>
results in
.PP
\ecopy
.PP
\copy
The second one is not valid output and will not be displayed by man.
This worked correctly in version 1.76.1, but no longer in version 1.77.0.
I checked in a fix for this. It should be in the next snapshot.