kerozin created an issue (kamailio/kamailio#4294)
Kamailio 5.7.4
When I write A new value to $fU pseudovariable it acttually appends, but not replace.
A from header before manipulation: sip:3451088@192.168.107.17
In failure route I do $fU = "77719365301";
The header after manipulation looks as: sip:345108877719365301@192.168.107.17
this behavior was reported in #3165 but closed. I believe this was happen by mistake.