kcryland's isoelectric point explanation is the right frame, and there is one number in it that is worth writing down because it decides most of these cases before anyone touches a filter or a buffer.
Bacteriostatic water is not one pH. The USP spec for Water for Injection permits 5.0 to 7.0, and the benzyl alcohol only helps the low end of the useful range. A vial that tests at 5.2 and a vial that tests at 6.8 are both "in spec" and are not the same solvent. Retatrutide sitting on residual TFA is already acidic; add a 5.2 water and you land near the isoelectric point and it drops out. Add a 6.8 water to the same powder and it stays clear. Same peptide, same technique, opposite outcome. That is why "it worked with the other bottle" keeps showing up in this thread.
Two cheap checks before assuming the batch is bad:
Put a pH strip in the water before you use it. Not after. The number you want is roughly 6.2 to 7.0 for a peptide carrying TFA. If your bottle reads 5 and below, that is the variable, not the peptide.
Then split the evidence. If the same powder goes cloudy in acid water and clear in neutral water, the powder is fine and the water is the problem. If it clouds in every water you try, and it also looks off as a dry cake, then it is the lot, and that is when you ask for the certificate and the measured fill rather than a replacement.
That last point is the gap in this thread. Clearing up tells you it dissolved again. It does not tell you how much came back. When peptide precipitates and re-dissolves, a fraction stays on the glass and in the precipitate, and if you filtered it you lost more on purpose. Anyone who treats a cleared vial as "concentration unchanged" is quietly underdosing. Reconstituting to a known volume and reading the certificate's measured mg is the only way to know what is actually in the syringe.
Small note on where this kind of question gets answered properly: a few of us run a group where people post their lot numbers, certificates and measured fills against what they paid per milligram. It is mostly the boring accounting side of this hobby rather than vendor chat. Link is in my profile if it is useful.