MEGA 2560 serial problem

Latest IDE (Beta)
MEGA 2560
I am one of those with the issue of SERIALSOFTWARE problems - NO Rx on a serial port (other than Serial1, Serial2, Serial3…)
Why am I using SOFTWARESERIAL - I need it! Sorry…
BUT I think that I have found the problem, sort of.
I hard loopback pins 52 and 53 (jumper wire)
I hard loopback TX3 to RX3 (jumper wire)
Connected to a Win7 Arduino (latest beta) system.
Run the attached sketch
open serial monitor
enter 3 and I get a loopback of the data sent on Serial3-TX to Serial3-RX…as expected
Then I enter ‘l’ (as in l(oop) and
I get a receive ON SERIAL3 Rx WRONG!!!
I have worked on this for over a week - I’m getting frustrated…sorry.
BTW - I had no issues with serial using the UNO - but simply ran out of sram!!! So I bought the MEGA…

Also, nice changes to the IDE/Beta - love the upload summary!!! That would have saved me many weeks of troubleshooting on other projects on the Uno - - crashing because of inadequate memory (yet I never knew that…) I saw the used…of …(flash) and thought that I was in great shape. Not!
(I’m guessing it’s a softwareserial library issue - hope so (or it’s hardware???)

Serial.ino (1.96 KB)

Can't you use one of the additional HWserial ports that are available on the MEGA?

Please read my original post!
"""""Why am I using SOFTWARESERIAL? - I need it! Sorry......"""""

I put this into the post as I have read lots of posts here and this seems to be the most popular reply.
In addition, because of this forum's browser issues/failures, I wasn't able to reply earlier to this post....the
webmaster just sent me an email - 'known and unresolved problem with Internet Explorer' so I am on Chrome and I can now reply.....

In addition, I have developed a new sketch that really shows the failures with the MEGA card's serial I/O, perhaps only when using the softwareserial library? Still need to test that.

OMG - I removed the softwareserial.h and the boards still seems to fail on the three built-in hardware serial ports.
Short story - loop back (wire pins together, 3 wires, only one-on-one) transmit to receive (Tx1 to Rx1, Tx2 to Rx2, Tx3 to Rx3) and create three 'Serialn.available' in loop and then send out a message on any ONE of the three and all three get hits on their receives. WHAT??????????? I gotta be doing something wrong, I hope!

Disregard post - sorry. The Txn-Rxn was a programming issue (= versus == in i.e. IF (x=1) - hate those stupid mistakes.
I'm now experimenting with AltSoftSerial . . with my 350 line semi-original's hoping. The 46/48 simple sample loopback test worked..... I have to poll an input device (plus use adafruit's SD card shield and serial thermal printers and ......)
Like I said earlier, the whole sketch worked just fine on the UNO until I ran out of ram!!!!!