I used to work for a defence contractor who avidly programmed everything in ADA with verified compilers and mathematically proved algorithms.
Stuff still broke because the algorithms and designs were wrong. That particular problem is far more problematic than type constraints.
Regarding BBC BASIC, it is strongly typed but all casts and conversions are implicit so you need to know what it's going to do:
REM win p%=4;q%=4;r%=p%/q%;PRINTr% REM fail p%=4;q=4.0;r%=p%/q;PRINTr%
When it goes wrong, it's not usually the code that's gone phut:
http://www.ntk.net/2000/07/14/dohtrain.jpg