Making "reply" to old message resets "first unread" pointer to the end of conversation

Running RiotWeb dev version
Time-to-time, not always:

Read log from a channel back to about 3 hour/300 messages.
Press "reply" on amessage menu, up right corner. Write reply, enter.

Result:
log jumps to the last message in channel, no "jump to first unread message" button.

Wanted result:
just keep first unread position in place. Allow me to continue reading and commenting of log.