I believe I found an issue with the patch 20170729. I've narrowed down the issue to the change in misc/terminfo.src. If it helps, here's a diff that fixes the issue for my terminal. If I knew terminfo better I would try to apply it only to xterm terminals that support ansi rep, but I am not that knowledgable on the subject.
diff --git a/misc/terminfo.src b/terminfo.src
index ae734f6f..dc9143f0 100644
--- a/misc/terminfo.src
+++ b/terminfo.src
@@ -4282,9 +4282,8 @@ xterm-xfree86|xterm terminal emulator (XFree86),
xterm-new|modern xterm terminal emulator,
npc,
indn=\E[%p1%dS, kb2=\EOE, kcbt=\E[Z, kent=\EOM,
- rin=\E[%p1%dT, use=ansi+rep, use=ansi+enq,
- use=xterm+pcfkeys, use=xterm+tmux, use=ecma+strikeout,
- use=xterm-basic,
+ rin=\E[%p1%dT, use=ansi+enq, use=xterm+pcfkeys,
+ use=xterm+tmux, use=ecma+strikeout, use=xterm-basic,
# This fragment is for people who cannot agree on what the backspace key
# should send.