At the powder drop:
Are you using a typical powder drop? If so, it's fine to weigh a bunch of individual charges to make sure you're not getting wild charge weight swings from one drop to the next, but just do ten individual charges once to check. To set your powder drop, weigh ten drops combined and divide by ten for your single charge weight. This gives you a little more precision on average drop weight. If you think your consecutive drops are 4.0 and 4.1, but they're actually an average of 3.97 and 4.13, that 1.6gr increase (average) is going to produce more velocity than expected when you think it's a .1gr increase.
Also, use check weights to adjust the beam scale again.
Tips to tighten up your chrono readings:
What were your chrono conditions? I am in sunny Florida, and the chrono works a lot better at 9:00AM with partly cloudy skies than it does at 1:00PM on a clear day.
I set up a target stand between the chrono and the sun, so that the target stand casts a shadow across both sensors.
Get your chrono sufficiently far from your pistol. Don't worry -- you're not going to hit it. Probably.
The shinier the bullet, the less consistent the chrono readings. Plated bullets are the shiniest and give the worst readings. Take a Sharpie and mark up the noses.
Also, regarding your results, there is a charge weight at which you will start getting a fast pressure seal. At this point, you usually see a bigger than average velocity jump because the chamber isn't losing any gas or powder that slips out between the case walls and chamber walls before the pressure seal is created. That could be a contributing factor.
Seriously, check your scale again. The biggest safety consideration here is that you're using more powder than you think you are. 4.1gr of W231 with a 124gr Berry's RN at 1.14 doesn't worry me at all. Also, keep in mind that even if your chrono is telling you right, going up to 4.3gr is going to put you into +P, but it's not going to blow up the gun. I'm not saying you want to make it your go-to load and run it thousands of it through your pistol, but 10 rounds isn't going to kill the gun. I've shot 4.6gr with a jacketed RN over-sized at .356.
I'll also tell you that as pressure keeps increasing past the point of the good pressure seal, you start getting diminishing returns on your powder. As you go up a ladder, you might see
3.9 -- 1000 ft/s
4.0 -- 1020 ft/s
4.1 -- 1040 ft/s
4.2 -- 1060 ft/s
4.3 -- 1070 ft/s
4.4 -- 1075 ft/s
If you see that, where the incremental increase in velocity starts dropping off as you keep going up in powder charge, THAT is when you need to stop dead in your tracks. If I get a 42 ft/s increase in velocity from a single tenth increase in powder, my response is "Whoo hoo! Plenty of head room left to go!"
Recheck your scale. Recheck your scale. Recheck your scale. Make bleeped sure your drop is dropping what you think it is. Then make up a full ladder again and retest. And weigh ten drops at a time to get a more precise average. Color your bullet tips with a Sharpie. Then chrono between 9:00 and 10:00 in the morning.