LimeSDR TX bandwidth setting incorrect

[milestone12]

For an application that I am currently working on I need to transmit chirp signals with a bandwidth of 15MHz.
The setup consists of a transmitting LimeSDR and a receiving LimeSDR that both operate at a sample rate of 32Msps.

I always set the RX bandwidth to 16MHz. Now, the waveforms and the spectrum that I expect look like this:

To achieve this, I usually set the TX bandwidth to 100e6.

However, if I assign TX bandwidth the values 16e6 or 32e6, I will get the following:

Can you please help me investigate that issue. It probably occurs at the interface of Pothos and the LMS7 module.
Thank you very much.