Question: Problem with Dsolve, error "unable to evaluate the partial derivatives of f(x,y) for stiff solution"

Hi,

I'm facing this issue when I try to use the Dsolve function in maple, it indicates me the following error :

"Error, (in dsolve/numeric/SC/firststep) unable to evaluate the partial derivatives of f(x,y) for stiff solution"

Here is part of the code :

Lagerkraft:=rhs(Eq__Sys_4_ohneZwang[1][2])=0;
                                      2           
                          / d        \            
Lagerkraft := cos(phi(t)) |--- phi(t)|  a__ks m__k
                          \ dt       /            

                             2             
                 / d        \              
   + cos(phi(t)) |--- phi(t)|  a__sss m__ss
                 \ dt       /              

                             2           
                 / d        \            
   + cos(phi(t)) |--- phi(t)|  l__k m__ko
                 \ dt       /            

                             2          
                 / d        \           
   + cos(phi(t)) |--- phi(t)|  l__k m__p
                 \ dt       /           

     /  2        \                       
     | d         |                       
   + |---- phi(t)| sin(phi(t)) a__ks m__k
     |   2       |                       
     \ dt        /                       

     /  2        \                         
     | d         |                         
   + |---- phi(t)| sin(phi(t)) a__sss m__ss
     |   2       |                         
     \ dt        /                         

     /  2        \                       
     | d         |                       
   + |---- phi(t)| sin(phi(t)) l__k m__ko
     |   2       |                       
     \ dt        /                       

     /  2        \                                      /      
     | d         |                                      |   4  
   + |---- phi(t)| sin(phi(t)) l__k m__p + 5000000 A exp|- --- 
     |   2       |                                      \  961 
     \ dt        /                                             

                                             2\                   
  /            /phi(t) + Pi\                \ |                   
  |100 Pi trunc|-----------| - 25 phi(t) + 9| | u + 200000 u A = 0
  \            \   4 Pi    /                / /                   


indets(Lagerkraft,name)
  {A, Pi, a__ks, a__sss, l__k, m__k, m__ko, m__p, m__ss, t, u}

Parameterliste__5:=[
A=4071.5*10^(-6),
a__ks=-20.94481*10^(-3),
a__kos=14.063837*10^(-3),
a__sss=0,
l__k=100*10^(-3),
m__k=11.02736,
m__ko=0.7237868,
m__p=1.437419,
m__ss=15,
u=1
];
                     [                                            
Parameterliste__5 := [A = 0.004071500000, a__ks = -0.02094481000, 
                     [                                            

                                             1                    
  a__kos = 0.01406383700, a__sss = 0, l__k = --, m__k = 11.02736, 
                                             10                   

                                                       ]
  m__ko = 0.7237868, m__p = 1.437419, m__ss = 15, u = 1]
                                                       ]


Lagerkraft5a:=subs(Parameterliste__5, Lagerkraft);
                                                        2
                                            / d        \ 
 Lagerkraft5a := -0.01484538000 cos(phi(t)) |--- phi(t)| 
                                            \ dt       / 

                                  /  2        \               
                                  | d         |               
    + 814.3000000 - 0.01484538000 |---- phi(t)| sin(phi(t)) + 
                                  |   2       |               
                                  \ dt        /               

                  /      
                  |   4  
   20357.50000 exp|- --- 
                  \  961 

                                              2\    
   /            /phi(t) + Pi\                \ |    
   |100 Pi trunc|-----------| - 25 phi(t) + 9| | = 0
   \            \   4 Pi    /                / /    


indets(Lagerkraft5a,name)
                            {Pi, t}

Lösung_Lagerkraft:=dsolve({Lagerkraft5a,AB},phi(t),numeric,dsolve_options);

Thanks