When neovim is opened in konsole and guicursor is set (to `guicursor=n-v-c-sm:block,i-ci-ve:ver25,r-cr-o:hor20,a:blinkon0` which is default) it is not possible to zoom any more using Ctrl + mouse wheel as the zoom level jumps back to the original level all the time. `:set guicursor=` fixes the problem, but then the cursor remains a block all the time (nvim usually sets the cursor to a beam when it is in insert mode). I think this bug may be related to Bug 347323 but I'm not sure.
Unable to reproduce with freshly built NVIM v0.5.0-64-gcb2520717 and konsole 19.11.70. My $TERM is xterm-256color, which may also be relevant.
I'm not able to reproduce it neither any more.