To be fair, these are not a good quality machine like your Olympia.  The later plastic-bodied version was even worse.  The alignment probably wasn't perfect when new.  I suspect that dropped 'a' might be you, although you are probably not aware that you are doing it.  You are probably 'glancing' the shift key when you go for the 'a', just nudging it enough to lift the carriage slightly and momentarily.  The typebars are mild steel on this model, not spring steel as found on better makes.  This means that you only have to clash a couple of typebars when typing, and they will deform and upset the alignment.  Because they are soft mild steel, you can carefully bend them back into shape - but - they seem to have a built-in weak point just under the typeface so they are easy to break too !  Uwe is right - there is definitely a problem with the shift.  For a start, it is out of adjustment, which is why the capital and small letters do not line up.  I really can't comment on why the carriage is sticking without seeing the machine and handling it.  To give you some idea of what I think of these machines generally - I buy and sell as well as doing repairs/servicing, and would never buy one in to sell on.  I don't think that they are reliable enough.  There is one exception.  I did come across a very late Smith-Corona Courier.  Probably the very last version of this machine before the factory in West Bromwich closed down in the late 1980's.  It seems that they finally got their act together just before they stopped production.  The Courier actually has spring steel typebars and the quality is much improved.  They had even abandoned the (now unobtainable) model-specific ribbon in favour of the standard spool which most Japanese portables take.  Still not 'German' quality, but perfectly acceptable as a 'starter' machine !