Angelina Jolie told her and Brad Pitt's children to avoid him like the plague during custody visits post-split -- so claims a guy who used to run security for them for years.

Brad's attorneys filed new legal docs Thursday in their ongoing winery case -- and they offer up a sworn declaration written by a man named Tony Webb ... who says he used to head up a security company that offered services to Brangelina while they were married.

In the docs, obtained by TMZ, Webb claims that in the aftermath of their divorce in 2016 -- and all the custody disputes that followed over their 6 shared children together -- he'd been hit up by Angie's personal assistant, who he says told him he heard 2 of Webb's security officers still working AJ's detail at that point, were going to testify in family court.

Long story short ... Webb claims that Angie's assistant told Webb to relay to the two officers who were going to take the stand that they'd signed NDAs with her, and that if they broke them ... she'd sue 'em. Webb says these two guys intended to testify if subpoenaed ... and then one of them made big claims about something he claimed to have overheard Jolie say to the kids.

According to Webb, the guard said he'd testify that he heard Angie telling the kids to not spend any time with Brad whenever they had to go to his place during his allotted time with them.

The whole point of bringing this up -- from Brad's lawyers perspective -- is to emphasize their argument that Jolie herself uses NDAs quite a lot ... and that she's allegedly tried "silencing" people with them before ... just like she claims Brad tried to do in connection with their wine deal that fell through.

Remember, the latest drama in the winery case is Angie claiming Brad tried to force her to sign a very restrictive NDA as part of the sale of her winery shares -- something he disputed ... and which he and his lawyers are now trying to poke holes in with this declaration.

As you know ... there's been a lot of mudslinging between these two amid their winery case -- not to mention their larger divorce case, which is still ongoing -- and here's the latest.

Brad has been said to have somewhat of a strained relationship with his kids ... and now, with this latest alleged anecdote, it would appear to explain why ... at least from her perspective.