Wow. So I did 100% Huel (or near enough) for about 6 months and lost about 30 lbs. Stopped when I got pregnant. Maybe had the occasional stinky Huel fart but nothing too bad, and never had any pooing problems either. Now baby is 4 months old and I’ve been back on the (nearly) 100% Huel for the past 6 weeks to try to lose the baby weight, and the farts are UNREAL!! Like, they’re so bad my husband is worried they’re going to suffocate the baby. And the poos were rivalling the baby’s mustardy masterpieces for a while there. I’m thinking it’s because I had a course of very broad spectrum antibiotics right after I gave birth—my first antibiotics since 1997. My poor gut microbiome! I’ve tried to build it back up with some kefir and fermented veg but it’s just not the same. I honestly don’t know if I can continue (seriously, this poor baby!!), which will really break my heart because it worked so well for me before! Anyone had any experience like this and did you find a way to improve things besides just giving it time?!
I don’t have this same experience (poor you)
But always take BioKult after a course of antibiotics. There are many probiotics out there to choose from, but that’s the one that I’ve personally found the most effective for resolving gastrointestinal problems.
Maybe take the max dose of probiotics for a good 3-4 weeks and then try again with the Huel, and build it up slowly starting with just 2 scoops a day for a week.
Pregnancy can also change all kinds of things - metabolism, gut biome, digestion. I know people that have suddenly developed allergies or intolerances to foods they used to be fine with. It can take a while for everything to reset back to how it was.
Personally I’ve found the only time I get digestive issues on huel is when I’m drinking lots of orange juice or eating citrus fruit alongside it. Bit bizarre. Not sure that’ll help you 
This is actually the one area of probiotics that has a decent amount of evidence.
Even supermarket probiotics such as Actimel and Yakult can help when your microbiome is depleted, such as after a course of antibiotics. They should help reduce the severity and duration of your symptoms.
This is an article to support the theory and also the use of probiotics. Not the best article by quality but quite easy to read. In general, antibiotics of any type target all bacteria and then in doing so target the intended bacterium causing the infection. It is the removal of the ‘probiotics’ that cause the symptoms you have described. This may continue for up to 4 weeks after your final course of antibiotics. In contrast, and in keeping with the clinical setting in which I engage, I must consider the NICE guidelines. They suggest in a ‘healthy’ person there should be no benefit in taking ‘probiotics’ because their depletion should naturally recover. Link attached for reading.
I am not suggesting you are ‘unhealthy’ but just providing thought.
How long have you been off the anti-biotics.
Sex hormones can also disrupt gut bacteria and these are prevalent in pregnancy and can take upto a year to dissipate. Also have you had any oral health issues during pregnancy?
I think I’ve just had my first bout of Huel farts. That was an interesting experience. 
A bit harsh giving up on your baby, I know Huel is good, but that good? 
Best poops I’ve ever had were after a period of mixing Biomel with Huel powder. Genuine urge to just stand up and salute the bowl some days, I was so proud. Can’t say it lasts forever after stopping the Biomel though.
Just wait, you’re gonna love it 
Probiotics are a little controversial but many people (myself included) have good results with them.
If you’re a baller, get VSL#3 which is shipped by courier in a refrigerated box and is about as potent as you can get. It’s also quite well studied and has been shown to be affective.
Otherwise, BioKult is really quite good indeed. It says it doesn’t need to be refrigerated but I still would just in case. Take that for a week and you’ll be doing dumps worthy of Instagram.