VOA: 《Republican Congressman Faces Blowback for Anti-Trump Stance》
A congressman is in our opinion gone off the rails and said things that we don't agree with.
The county Republican Party in Kinzinger's district recently voted to censure him.
What he's been saying about our former president and his supporters and a lot of conservative republicans is not okay.
请教老师：上面出现的gone off the rails到底应该是 have/has gone off the rails 还是 be gone off the rails ? 这二者都可用，有不同吗？
还有，What he's been saying...假如换用What he's said 含义有不同吗？
词典例句：
He's gone off with my passport. 他拿走了我的护照。
这里到底是 is 还是 has 呢？
早期英语中，he's gone中的’s, 是不分has或is的，二者通用。现代英语则把is gone剖析为系表结构，把has gone剖析为目前完成时。二者意思基本相同。
has been saying 目前完成进行时，表示一直在说。has said, 为目前完成时，表示说过。意思当然不同。
He's gone off with my passport. 理解为is或has都是可以的。根据现代英语，以理解为has gone目前完成时更好，强调护照目前不在我手中。过去动作对目前的影响。