There is no avenue in synthesis or purification in which LSD and strychnine would come into contact. There is no benefit to cut LSD with strychnine. The amount of strychnine necessary to have any effects on humans is too close to the lower end of lethality to be a useful cutting agent.
That being said, there are side-products in LSD synthesis or purification from natural substances (e.g. ergot fungus cultures) can leave related substances as impurities. These can cause vasoconstriction, which is unpleasant. This isn't strychnine, and it's unlikely to be dangerous as small amounts of impurity. It doesn't feel very nice, and it can cause bruising. Or, people tripping can just bump into things and be clumsy. Either way, the explanation that this comes from strychnine is and has always been bunk.
It should be obvious, but please don't confuse any of this with an endorsement of the drug. That's a separate topic. The most I'll say here is that I don't recommend it.
