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Subscripting an array ‘x’ without dimnames by a ‘length(dim(x))’-column character matrix gave "random" non-sense, now an error; reported in PR#18244 by Mikael Jagan.
Initialization of self-starting ‘nls()’ models with initialization functions following the pre-R-4.1.0 API (without the ‘...’ argument) works again for now, with a deprecation warning.