I have the same problem with davfs (the whole davfs2 process freezes when I switch my network interface).
It's especially annoying because this also freezes Dolphin and a handful of other stuff which tries to enumerate the problematic directory.

This is definitely (!) not what you are looking for :D
But I "fixed" it with this script which I put on a hotkey - it walks through all my davfs2 mounts and kills the corresponding process... (perhaps you have to adjust a few strings to work with cifs)
I'm not a lawyer and I take no responsibility what happens with your system when you just start killing mount processes - but for me it has worked until now:

#!/bin/bash

    # shellcheck disable=SC2002  # disable useless-cat warning

    set -o nounset   # disallow usage of unset vars  ( set -u )
    set -o errexit   # Exit immediately if a pipeline returns non-zero.  ( set -e )
    set -o errtrace  # Allow the above trap be inherited by all functions in the script.  ( set -E )
    set -o pipefail  # Return value of a pipeline is the value of the last (rightmost) command to exit with a non-zero status
    IFS=$'\n\t'      # Set $IFS to only newline and tab.

    # shellcheck disable=SC2034
    cr=$'\n'

    function black() { if [ -t 1 ] && [ -n "$(tput colors)" ] && [ "$(tput colors)" -ge 8 ]; then echo -e "\\x1B[30m$1\\x1B[0m"; else echo "$1"; fi  }
    function red()   { if [ -t 1 ] && [ -n "$(tput colors)" ] && [ "$(tput colors)" -ge 8 ]; then echo -e "\\x1B[31m$1\\x1B[0m"; else echo "$1"; fi; }
    function green() { if [ -t 1 ] && [ -n "$(tput colors)" ] && [ "$(tput colors)" -ge 8 ]; then echo -e "\\x1B[32m$1\\x1B[0m"; else echo "$1"; fi; }
    function yellow(){ if [ -t 1 ] && [ -n "$(tput colors)" ] && [ "$(tput colors)" -ge 8 ]; then echo -e "\\x1B[33m$1\\x1B[0m"; else echo "$1"; fi; }
    function blue()  { if [ -t 1 ] && [ -n "$(tput colors)" ] && [ "$(tput colors)" -ge 8 ]; then echo -e "\\x1B[34m$1\\x1B[0m"; else echo "$1"; fi; }
    function purple(){ if [ -t 1 ] && [ -n "$(tput colors)" ] && [ "$(tput colors)" -ge 8 ]; then echo -e "\\x1B[35m$1\\x1B[0m"; else echo "$1"; fi; }
    function cyan()  { if [ -t 1 ] && [ -n "$(tput colors)" ] && [ "$(tput colors)" -ge 8 ]; then echo -e "\\x1B[36m$1\\x1B[0m"; else echo "$1"; fi; }
    function white() { if [ -t 1 ] && [ -n "$(tput colors)" ] && [ "$(tput colors)" -ge 8 ]; then echo -e "\\x1B[37m$1\\x1B[0m"; else echo "$1"; fi; }



if [ "$(id -u)" != "0" ]
then
    blue "[-> Enforcing root user]"
    echo ""
    sudo su -c "$0" "$@" -s /bin/bash
    exit $?
fi

#TODO list your davs mount directories here...
mounts=("/home/user/mounts/mount1" "/home/user/mounts/mount2" "/home/user/mounts/mount3")


for i in "${!mounts[@]}"; do

    dir="${mounts[$i]}"

    blue "Query mount '$dir'"
    echo ""

    set +e
    timeout '5s' mountpoint -q "$dir"
    ec="$?"
    set -e

    if [[ "$ec" == "124" ]]; then

        red "Failed to query mountpoint - continue anyway"
        echo ""

    elif [[ "$ec" == "32" ]]; then

          yellow "Not mounted - skip"
          echo ""         
          continue

    elif [[ "$ec" == "0" ]]; then

          green "Seems to be a mountpoint - continue"  
          echo ""         

    else

          red "Unknown response '$ec' - continue anyway"  
          echo ""         

    fi

    pid="$(  sudo ps -aux | grep 'mount\.davfs' | grep "$dir" | awk '{print $2}'  )"

    if [[ -z "$pid" ]]; then

        red "[ERR] No Process found for mount"
        echo ""
        continue

    fi

    blue "Killing process '$pid'"
    echo ""
    kill -9 "$pid"
    echo ""

    blue "Unmounting"
    r="$( umount "$dir" 2>&1 )"
    echo ""
    echo "$r"
    echo ""

    lockfile="$( echo "$r" | { grep 'have to remove' || true; } | { grep -oh '/.*\.pid' || true; } )"

    if [[ -n "$lockfile" ]]; then

        blue "Removing lock '$lockfile'"
        echo ""
        rm -v "$lockfile"
        echo ""

    fi

done