Why does Marlin continue sending echo :busy: processing whenever I try to start a print?

Okay, I'm running the most up to date version of Marlin on my Mini Rambo, and I'm trying to figure out why it takes so long for my prints to start. I'm thinking that Marlin is processing the whole print file or something similar, requiring all of the processing power available, but I could be wrong. Is there any way to prevent this from happening? Or am I stuck having to wait forever for Marlin to decide to start my print? Thanks in advance.

Its normally waiting for the bed to come to temp..

Watch the temperatures

It might be waiting for the home position to be reached. Are all your endstops connected? can you home the printer manually?

I have the same issue and I am sure the two suggestions offered above are not correct. I get "busy processing" after I replaced a regular Rambo with a miniRambo and made the necessary configuration changes to support that board.. I get it when the hot end is already homed and the bed and hotend temp are where they should be. I will wait anywhere from 15 seconds to a minute for the print to start. Not the end of days, but It is definitely annoying.

Looking threw the code I see

#if ENABLED(HOST_KEEPALIVE_FEATURE)
/**
* Output a "busy" message at regular intervals
* while the machine is not accepting commands.
*/
void host_keepalive() {
millis_t ms = millis();
if (host_keepalive_interval && busy_state != NOT_BUSY) {
if (PENDING(ms, next_busy_signal_ms)) return;
switch (busy_state) {
case IN_HANDLER:
case IN_PROCESS:
SERIAL_ECHO_START;
SERIAL_ECHOLNPGM(MSG_BUSY_PROCESSING);
break;

and

language.h:#define MSG_BUSY_PROCESSING "busy: processing"

So. If you have enabled the HOST_KEEPALIVE_FEATURE then when busy_state = IN_PROCESS it will print that message

Im not sure what command set this flag, but im sure both of the heat and wait commands will.

If its not working for you try disabling the HOST_KEEPALIVE_FEATURE