Homing Additional Axes in 7 Axis Machine Issue and Checksum Errors

Since I needed to simultaneously move two separate gantries, I edited the marlin firmware so that it would support additional axis (x,y,z,e,u,v,w). I am now having issues with homing the V and W axis (homing of U is not needed). I am getting no response when I enter G28 V or G28 W. However, entering G28 causes homing of the X,Y,Z axis; this tells me it is recognizing the V axis, but not initiating the movement for whatever reason. I think the error is in the homeaxis function (marlin_main.cpp line~1180); the only other possible area is the case G28 section (marlin_main.cpp line~1437). I do recognize I can use the G1 command to move the V and W axis until the endstop is hit; then use the command G92 to simulate homing for these axis. My ability to not locate the error is just bothering me. Any idea what I am doing wrong?

In a separate issue, I am getting errors in the repetier-host log that don't seem to be affecting anything as of right now. The three errors that pop up spontaneously are: 1.) "No checksum with line number" ; 2.) "Line Number is not last line number" and 3.) "Checksum mismatch". These errors are being activated from the get_command function (marlin_main.cpp line~673). Should I be concerned with these errors? How would I go about fixing it?

Some other information that might be helpful is that I am using repetier-host as my software and my board is an AZTEEG X3 PRO. I attached marlin firmware files that I feel might be relevant. I appreciate any help or feedback that anyone might provide.

Modifying Line 1214 in marlin_main.cpp enabled me to fix the homing issue though the solution is non-ideal. Any idea why the second line below is causing the previously mentioned issue? Here it is:
destination[axis] = 750 * -1; //this works for some odd reason
// destination[axis] = 1.5 * max_length(axis) * axis_home_dir; //this does not work; not creating array like it is supposed to?

When I hit G28, all the axis home. the v and w axis are at a random number so I have to manually reset them to zero using G92.

In a possibly related issue, the repetier-host software running this 7 axis board tends to freeze up every once in a while. It occurs even more so when I have another repetier-host open and controlling a separate 5 axis board. My baud rate is 250,000. I realize that increasing this might help, but I figured I would at least mention it.

Most likely you missed some code in another source file. I would say somewhere the info max_length(axis) needs is not being set correctly.

If you are having communication errors, setting a lower baud rate will help. Not all hardware will work fine at 250000, so set it to 115200.