Perhaps I have misunderstood what you are trying to do. You can type your own choice of amplification inot either of the linked boxes in Amplify. One of your later posts suggests that you are now doing this.What I'm trying to do of course (as my last edit prior to exporting) is increase the volume to around -1.0 area.......but, the amplify command won't allow that.
It sounds as if your problem is simply the result of an Amplify step taking you to exactly 0dB, and where the waveform touches this level it is flagged as clipping, although it has not been damaged. Apparently some DACs don't like handling a signal that actually reaches 0dB, which is why you are advised to back off a bit from that level.
You ask about weather in the UK. It has been raining since late May, with daytime temperatures seldom reaching 20deg.C (68deg.F).