I just used flexible resin sometimes and all times I printed with it the first layers are bigger than the rest of the print, they look like have been more exposed to the laser, there is a way of fixing this?
Are you printing these directly on the build platform? The first couple millimeters of a print are overexposed and compressed to improve adhesion to the platform. Usually, the support base compensates for this but if you’re printing flat on the build platform, you might notice differences in the first couple of mm.