Yes, they sound like bat wing flaps. I have similar wide-spectrum flaps in my Audiomoth recordings and, in those rare cases I have recorded ultrasound, it is associated with flaps. To get flaps the bat of course needs to be quite close to the recorder.
Then there is Photedes minima (Small Dotted Puff as you say). O. fasciuncula seems to vary with its whitish border. And I have a feeling of missing an obvious species but maybe that was one of those two, don't know.
See Zach’s Recorder Recommendations – Zach Poff
It points to Zoom H5.
Another review: Macaulay Library Audio Gear Review
And with respect to migration, maybe the Nocmig equipment options at https://nocmig.com/equipment/.