Tileable Image - Rescaling Issue with Alpha Channel

Hi,

I work in game development, where it's common to use tileable textures that include additional information stored in the alpha channel of an image. For instance, we often assign the RGB channels to albedo data and reserve the alpha channel for roughness data.

Recently, we encountered an issue with the alpha channel of our textures. When downscaling the image in Photoshop (using "Bicubic Sharper" or other similar algorithms), the alpha channel displays visible seams along the edges. Interestingly, this problem does not affect the RGB channels, which scale down without any issues.

I suspect that the problem relates to the algorithm's handling of neighboring pixels, though it seems the alpha channel is processed differently than the RGB channels.
This poses a significant challenge, as our designers frequently need to downscale numerous textures. Is there a solution or an effective workaround for this issue? Unfortunately, using bilinear rescaling is not a viable option, as it results in overly blurred textures.

Thank you.