Performance Regression with Terrain Flattening Re-Grid

Hi all. I just wanted to note that there seems to be a significant performance regression with the Terrain Flattening routine after version S1TBX v6.0.3

When using the ‘re-grid method = True’ the following performance was noted between versions (times are for entire processing chain for two assembled slices):
v6.0.3 = 1h 15m
v6.0.5 = 4h 15m

‘regrid = False’ seems to be unaffected.

The resulting data of both appear to be similar, but pixel values vary slightly, implying there has been some change to the routine. Additionally, the terminal output now prints a large amount of the following lines when doing the correction:

x = 2440.0, y = 420.0, lat = 54.249826797897356, lon = -4.856447786383597, iter = 1, x' = 2440.0088500976562, y' = 420.00657359566435
x = 2460.0, y = 420.0, lat = 54.25018262793482, lon = -4.853443432414015, iter = 1, x' = 2460.0003089904785, y' = 420.00683590245256
x = 2480.0, y = 420.0, lat = 54.25053837834226, lon = -4.8504390507663615, iter = 1, x' = 2479.991767883301, y' = 420.0070982092408

I read that there is expected to be a re-work of the terrain flattening routine at some point in the future, but ideally I’d like to reduce processing time as soon as possible to the previous state.

Is there anywhere that I can see the changelog for minor version releases? I would like to know what has been updated to this routine since 6.0.3

Also, is there any way of rolling back the toolbox to a specific version? Though I realise this might not be advised if the latest version includes other fixes.

I have found that SNAP and the S1 Toolbox can be downgraded by changing the Plugin URL to any version of updates.xml.gz here. (One would probably have to uninstall the current version, if newer, and reinstall.) Though of course I wouldn’t recommend doing this generally as other important updates could be missed.

I have managed to determine that the slowdown to Terrain Flattening was introduced in s1tbx v6.0.5. I’m not sure if this is an unexpected problem, or an intended change to the operation that would improve the output. Either way, is it likely that this will be reverted/optimised soon in future updates?