The problem seems to be a difference between the released version of the MixedModels package (v2.3.0) and the master branch on the repository (v3.0.0-DEV). In v2.3.0 the estimated standard deviation of the random effects is over 6 in the model with the interaction term

```
$ julia-1.4.2 --project
_
_ _ _(_)_ | Documentation: https://docs.julialang.org
(_) | (_) (_) |
_ _ _| |_ __ _ | Type "?" for help, "]?" for Pkg help.
| | | | | | |/ _` | |
| | |_| | | | (_| | | Version 1.4.2 (2020-05-23)
_/ |\__'_|_|_|\__'_| | Official https://julialang.org/ release
|__/ |
(tmp) pkg> st
Status `/tmp/Project.toml`
[a93c6f00] DataFrames v0.21.3
[ff71e718] MixedModels v2.3.0
[6f49c342] RCall v0.13.7
julia> using DataFrames, MixedModels, RCall
julia> titanic = filter(:Freq => !iszero, rcopy(R"as.data.frame(datasets::Titanic)"));
julia> const GLMM = GeneralizedLinearMixedModel;
julia> form = @formula Survived ~ 1 + Age*Sex + (1|Class);
julia> m = fit(GLMM, form, titanic, Bernoulli(), wts=titanic.Freq, nAGQ=3)
Generalized Linear Mixed Model fit by maximum likelihood (nAGQ = 3)
Survived ~ 1 + Age + Sex + Age & Sex + (1 | Class)
Distribution: Bernoulli{Float64}
Link: LogitLink()
Deviance: 2210.0492
Variance components:
Column Variance Std.Dev.
Class (Intercept) 37.752020 6.144267
Number of obs: 24; levels of grouping factors: 4
Fixed-effects parameters:
ββββββββββββββββββββββββββββββββββββββββββββββββββββββββββββββββββ
Estimate Std.Error z value P(>|z|)
ββββββββββββββββββββββββββββββββββββββββββββββββββββββββββββββββββ
(Intercept) 0.423055 4.02214 0.105182 0.9162
Age: Adult -1.77117 2.73242 -0.648208 0.5169
Sex: Female 0.715531 3.93831 0.181685 0.8558
Age: Adult & Sex: Female 1.89466 4.19524 0.451621 0.6515
ββββββββββββββββββββββββββββββββββββββββββββββββββββββββββββββββββ
```

whereas in v3.0.0-DEV (which requires Julia-v1.4.0 or later)

```
$ julia-1.4.2 --project
_
_ _ _(_)_ | Documentation: https://docs.julialang.org
(_) | (_) (_) |
_ _ _| |_ __ _ | Type "?" for help, "]?" for Pkg help.
| | | | | | |/ _` | |
| | |_| | | | (_| | | Version 1.4.2 (2020-05-23)
_/ |\__'_|_|_|\__'_| | Official https://julialang.org/ release
|__/ |
(tmp) pkg> add MixedModels#master
Updating git-repo `https://github.com/JuliaStats/MixedModels.jl.git`
Updating registry at `~/.julia/registries/General`
Updating git-repo `https://github.com/JuliaRegistries/General.git`
Resolving package versions...
Updating `/tmp/Project.toml`
[ff71e718] β MixedModels v2.3.0 β v3.0.0-DEV #master (https://github.com/JuliaStats/MixedModels.jl.git)
Updating `/tmp/Manifest.toml`
[69666777] + Arrow v0.2.4
[becb17da] + Feather v0.5.6
[53afe959] + FlatBuffers v0.5.4
[ff71e718] β MixedModels v2.3.0 β v3.0.0-DEV #master (https://github.com/JuliaStats/MixedModels.jl.git)
(tmp) pkg> st
Status `/tmp/Project.toml`
[a93c6f00] DataFrames v0.21.3
[ff71e718] MixedModels v3.0.0-DEV #master (https://github.com/JuliaStats/MixedModels.jl.git)
[6f49c342] RCall v0.13.7
julia> using DataFrames, MixedModels, RCall
[ Info: Precompiling MixedModels [ff71e718-51f3-5ec2-a782-8ffcbfa3c316]
julia> titanic = filter(:Freq => !iszero, rcopy(R"as.data.frame(datasets::Titanic)"));
julia> const GLMM = GeneralizedLinearMixedModel;
julia> form = @formula Survived ~ 1 + Age*Sex + (1|Class);
julia> m = fit(GLMM, form, titanic, Bernoulli(), wts=titanic.Freq, nAGQ=3)
Generalized Linear Mixed Model fit by maximum likelihood (nAGQ = 3)
Survived ~ 1 + Age + Sex + Age & Sex + (1 | Class)
Distribution: Bernoulli{Float64}
Link: LogitLink()
Deviance: 2210.0492
Variance components:
Column Variance Std.Dev.
Class (Intercept) 0.40044704 0.63280885
Number of obs: 24; levels of grouping factors: 4
Fixed-effects parameters:
ββββββββββββββββββββββββββββββββββββββββββββββββββββββββββββββββ
Estimate Std.Error z value P(>|z|)
ββββββββββββββββββββββββββββββββββββββββββββββββββββββββββββββββ
(Intercept) 0.422887 0.414341 1.02 0.3074
Age: Adult -1.77117 0.281569 -6.29 <1e-9
Sex: Female 0.715344 0.405834 1.76 0.0780
Age: Adult & Sex: Female 1.89475 0.432309 4.38 <1e-4
ββββββββββββββββββββββββββββββββββββββββββββββββββββββββββββββββ
```

Sorry that this took so long to straighten out. I guess we better get v3.0.0 released soon.