I don't know usually that happens only in yellow map...because NPC have speed and long range and if you don't have BIG HP you will probably get sunk...it also depends if when the bot finish a wave with low hp,the next wave will automatic start with the LOW HP from the last wave that is already done...he will try to go in repair point but maybe he won't have enough time because all the NPC will shoot him at the beginning of the wave...so he gets SUNK...don't forget that flash player can block for a time so again he get will get sunk.
As you can see in my original post i mention that this bot WILL NOT WORK FOR EVERYBODY...I can't help you to fix it because i don't know how...I can only share what i know.
GOOD LUCK ON FIXING IT.