Hello,
The VSWR of an antenna only depends on that antenna, so if the transmitter's output impedance changes, VSWR should not change.
Sometimes VSWR becomes worse due to increased harmonic (or spurious) production of the final power stage.
Also many VSWR indicators show too optimistic VSWR values at low power, because of the diode voltage drop. When you increase the RF input power (to the antenna + VSWR indicator), VSWR indication will increase and will be more close to the real value of the antenna's VSWR.
So If you didn't change frequency, didn't change output power towards the vswr indicator and you are sure the antenna is still the same as before, your transceiver very likely produces too much harmonics or spurious.
As you changed PIN/band switching diodes in the output path, harmonic production may change.