Expect with ssh not working every time - bash

Question

I created script with expect + ssh + bash executed command to automate some process on remote machine.
Problem is that it is not working everytime.
Sometimes it hangs on password:
Sometimes it logins properly but do not execute remote command, just exit after timeout.
Here bash is script:
#!/bin/bash
USER="user"
PASSWORD="password"
MACHINES="host1 host2 host3 host4"
ex() {
expect -c "
log_file ${MACHINE}.log;#
set timeout 8;
spawn ssh $USER#$MACHINE
expect -re \".*ssword: \" {send \"$PASSWORD\n\"}
expect -re \".*host-.* \" { send \"sudo su -\r\"}
expect -re \".*user: \" { send \"$PASSWORD\r\"}
expect -re \".*# \" { send \"/usr/local/bin/REMOTE.COMMAND.sh\r\"}
expect -re \".*# \" { send \"exit\r\"}
expect -re \".*host-.* \" { send \"exit\r\"}
"
}
machines() {
for MACHINE in $MACHINES ; do
ex &
sleep 0.5
done
}
machines
Here is my working solution - if there is something wrong/not efficient comment please:
#!/bin/bash
USER="user"
PASSWORD="password"
MACHINES="host1 host2 host3 host4"
ex() {
expect -c "
log_file ${MACHINE}.log;#
match_max 100000;
set timeout 30;
spawn ssh $USER#$MACHINE
expect {
-re \".*ssword: \" {send \"$PASSWORD\r\"; exp_continue }
-re \".*user#host-.*\" { send \"sudo su -\r\"; exp_continue }
-re \".*ssword.*:.*\" {send \"$PASSWORD\r\"; exp_continue }
-re \".*host-.*# \" { send \"/usr/local/bin/REMOTE.COMMAND.sh\r\"; }
}
expect {
-re \".*host-.*# \" { send \"exit\r\"; }
}
expect {
-re \".*user#host-.*\" { send \"exit\r\"; }
}
"
}
machines() {
for MACHINE in $MACHINES ; do
ex &
sleep 0.5
done
}
machines

Answer 1

I had some similar problem once.
The problem was due to my SSH usage history, and my ~/.ssh/known_hosts data.
You should try add options to your SSH command, so that it always behave the same wether you have already connected the host or not.
For example :
ssh -o PreferredAuthentications=publickey -o StrictHostKeyChecking=no
You might want to use different kind of authentication with option PubkeyAuthentication.

Answer 2

Try this?:
expect -c "
log_file ${MACHINE}.log;#
set timeout 8;
spawn ssh $USER#$MACHINE
expect {
-re \".*ssword: \" {send \"$PASSWORD\n\";exp_continue}
-re \".*host-.* \" { send \"sudo su -\r\";exp_continue}
-re \".*user: \" { send \"$PASSWORD\r\";exp_continue}
-re \".*# \" { send \"/usr/local/bin/REMOTE.COMMAND.sh\r\";exp_continue}
-re \".*# \" { send \"exit\r\"}
-re \".*host-.* \" { send \"exit\r\"}
}
"
Besides, I have never used expect in a background process.