Sounds like you've solved the problem but in case other people are looking for ways to create 4096-sample waveforms, there are several approaches that would work. First thing is to check whether the Sound you're using actually requires a 4096-sample wavetable. If it does, then here are some approaches:
• In the Wave editor, select the waveform, then Modify> Change duration to 4096. If this wavetable is intended for use as one cycle in an Oscillator, choose Modify>Make cycle
• If you are creating the wavetables on the fly, you could play the sample with a FunctionGenerator with the Duration set to 4096 samp feeding into a DiskRecorder (or use it immediately using a MemoryWriter/reader combination). If you have a lot of files to extend, you could apply Action>Batch processing to this Sound.